iDev: UIImage and UIImage View

When we use images in our application then we face different type of scenarios while handling the image. Before we go into the scenarios / situations of image handling in Application, let us understand the concept of UIImage and UIImageView.

Concept of UIImage and UIImageView (container)

UIImage – Bitmap with different formats Ex png and jpeg. Recommended format is png.UIImageView – This is an iOS Widget that acts like a container for holding the image. To hold the image, UIImageView is required.

When UIImage is shown in UIImageView, there is a property (Content Mode) of UIImageView, that render the Image in UIImageView. We mostly use three types of Content Mode property. These are:

  • Scale To Fill
  • Aspect Fit
  • Aspect Fill

How these Content Mode render the image we can see by following examples

  • UIImage of size (100×150)
  • UIImageView of size (200×200)

Different Content modes for placing Image in ImageView

1. Scale To Fill

In this case, content is scaled to fill in ImageView with distorted or same aspect ratio. If the image aspect ratio is different than that of container then final image ratio when fitted in the container will be different and hence the image is finally distorted.

(Aspect Ratio is Width / Height)

InnovationM Image Handling in iOS

2. Aspect Fit

In this case, content is scaled to fit in ImageView (container) without changing the aspect ratio of image . Remainder is transparent.

InnovationM Image Handling in iOS

3. Aspect Fill Without Clipping

In this case, image is scaled to fill in ImageView. Aspect ratio of image is not changed.

InnovationM Image Handling in iOS

4. Aspect Fill With Clipping

In this case, content is scaled to fill in ImageView the same way it happen in the above case but then finally image is cropped to the exact size of the ImageView size.

InnovationM Image Handling in iOS

Calculating new width and height with maintaining aspect ratio

Image original width = 100 and height = 150
Container width  = 200 and height = 200

x-ratio = Container width / Image original width = 200/100 = 2.0
y-ratio =  Container height / Image original height = 200/ 150 =  1.33

Selected ratio = min (x-ratio, y-ratio) = 1.33

Final Image width = Image original width * Selected Ratio = 100 * 1.33 = 133
Final Image height = Image original height * Selected Ratio = 150 * 1.33 = 200

Final Image width x height = 133 x 200 (Original width x height of image was 100 x 150)

Showing Images coming from Server (Different Scenarios)

We can use Aspect Fit mode for all the scenarios. It will serve in every scenario if you don’t want to distort image.

Scenario 1
Image width is lesser than Container width.
Image height is lesser than Container height

Image width = 100 and height = 150
UIImageView width = 200 and height = 200

Final Image width = 133  and height = 200 (Refer the calculations above)
Image is scaled up to fit the container.

InnovationM Image Handling in iOS

Scenario 2 
Image width is greater than Container width.
Image height is lesser than Container height

Image width = 100 and height = 150
UIImageView width = 80 and height = 200

Final Image width = 80 and height = 122
Image is scaled down to fit the container.

InnovationM Image Handling in iOS

Scenario 3
Image width is lesser than Container width.
Image height is greater than Container height.

Image width = 100 and height = 150
UIImageView width = 200 and height = 120

Final width = 80  and height = 120
Image is scaled down to fit the container.
InnovationM Image Handling in iOS

Scenario 4
Image width is greater than Container width.
Image height is greater than Container height.

Image width = 100 and height = 150
UIImageView width = 80 and height = 100

Final width = 66  and height = 100
Image is scaled down to fit the container.

InnovationM Image Handling in iOS

Scenario 5 (Same Aspect Ratio of Image and ImageView)
Image width is greater than Container width.
Image height is greater than Container height.

Image width = 100 and height = 150
UIImageView width = 80 and height = 120

Final width = 80 and height = 120
Image is scaled down to fit the container.

InnovationM Image Handling in iOS

Scenario 6 (Same Aspect Ratio of Image and ImageView)
Image width is lesser than Container width.
Image height is lesser than Container height.

Image width = 100 and height = 150
UIImageView width = 120 and height = 180

Final width = 120 and height = 180
Image is scaled up to fit the container.

InnovationM Image Handling in iOS

How we change the image size and compress image file size-

Uploading Images to the Server (Different Scenarios)

Many times we have to upload images in an application from device (iPhone, iPad) to the server. It could be a photo clicked from the camera or there was an old image that we choose and upload from the application.

Before uploading we can do two things with the image:

1. Change the width and height of original image.
2. Compress the image to be of smaller file size.

Let us understand them.

1. Change the width and height of original image.

To resize the image, we have to configure the drawing environment for rendering into a bitmap.

1# UIGraphicsBeginImageContextWithOptions()  method is used to create the bitmap-based graphics context.

This method takes two parameters:

  1. Size of image (changed size) and
  2. Scale factor of device as parameter.

Scale factor for Normal Display = 1.0
Scale factor for Retina Display = 2.0

2# – (void) drawInRect:(CGRect)rect; method is used to draw the image in target rectangle.

3# UIGraphicsGetImageFromCurrentImageContext()  method is used to get the resized image from drawing environment.

4# UIGraphicsEndImageContext() method is used to clean up the bitmap drawing environment and remove the graphics context from the top of the context stack.

Example :

Original source Image  Size = (2448, 3264)
Original source image file size = 3.8 MB

After resizing image to size (1024,768):
Resized source Image  Size = (1024,768)
Resized source image file size = 2.0 MB

Code Example:

2. Compress the image to be of smaller file size.

We can compress the image file size by following method.

UIImageJPEGRepresentation() This method takes two parameter

  1. UIImage object.
  2. Compress ratio (It can be between 0.0 and 1.0)

This method will return NSData representation of image after compressing.

Example :

Original source Image  Size = (2448, 3264)
Original source image file size = 3.8 MB

After compressing image file  size by 0.5:
Resized source Image  Size = (2448, 3264)
Resized source image file size = 534 KB

Code Example:

Depending upon your requirement whether to reduce the size (width and height in pixels) OR reduce the file size OR Both, you may apply the above.

Original Source: Click Here

iDev: Set Warnings in Xcode

Here a reference docs, How we set the warnings in Xcode and get the results :

Source Link: Click Here

Warnings are diagnostic messages that report constructions that are not inherently erroneous but that are risky or suggest there may have been an error.

The following language-independent options do not enable specific warnings but control the kinds of diagnostics produced by GCC.

Check the code for syntax errors, but don’t do anything beyond that.
Limits the maximum number of error messages to n, at which point GCC bails out rather than attempting to continue processing the source code. If n is 0 (the default), there is no limit on the number of error messages produced. If -Wfatal-errors is also specified, then -Wfatal-errors takes precedence over this option.
Inhibit all warning messages.
Make all warnings into errors.
Make the specified warning into an error. The specifier for a warning is appended; for example -Werror=switch turns the warnings controlled by -Wswitch into errors. This switch takes a negative form, to be used to negate -Werror for specific warnings; for example -Wno-error=switch makes -Wswitch warnings not be errors, even when -Werror is in effect.The warning message for each controllable warning includes the option that controls the warning. That option can then be used with -Werror= and -Wno-error= as described above. (Printing of the option in the warning message can be disabled using the -fno-diagnostics-show-option flag.)

Note that specifying -Werror=foo automatically implies -Wfoo. However, -Wno-error=foo does not imply anything.

This option causes the compiler to abort compilation on the first error occurred rather than trying to keep going and printing further error messages.

You can request many specific warnings with options beginning with ‘-W’, for example -Wimplicit to request warnings on implicit declarations. Each of these specific warning options also has a negative form beginning ‘-Wno-’ to turn off warnings; for example, -Wno-implicit. This manual lists only one of the two forms, whichever is not the default. For further language-specific options also refer to C++ Dialect Options and Objective-C and Objective-C++ Dialect Options.

Some options, such as -Wall and -Wextra, turn on other options, such as -Wunused, which may turn on further options, such as -Wunused-value. The combined effect of positive and negative forms is that more specific options have priority over less specific ones, independently of their position in the command-line. For options of the same specificity, the last one takes effect. Options enabled or disabled via pragmas (see Diagnostic Pragmas) take effect as if they appeared at the end of the command-line.

When an unrecognized warning option is requested (e.g., -Wunknown-warning), GCC emits a diagnostic stating that the option is not recognized. However, if the -Wno- form is used, the behavior is slightly different: no diagnostic is produced for -Wno-unknown-warning unless other diagnostics are being produced. This allows the use of new -Wno- options with old compilers, but if something goes wrong, the compiler warns that an unrecognized option is present.

Issue all the warnings demanded by strict ISO C and ISO C++; reject all programs that use forbidden extensions, and some other programs that do not follow ISO C and ISO C++. For ISO C, follows the version of the ISO C standard specified by any -std option used.Valid ISO C and ISO C++ programs should compile properly with or without this option (though a rare few require -ansi or a -std option specifying the required version of ISO C). However, without this option, certain GNU extensions and traditional C and C++ features are supported as well. With this option, they are rejected.

-Wpedantic does not cause warning messages for use of the alternate keywords whose names begin and end with ‘__’. Pedantic warnings are also disabled in the expression that follows __extension__. However, only system header files should use these escape routes; application programs should avoid them. See Alternate Keywords.

Some users try to use -Wpedantic to check programs for strict ISO C conformance. They soon find that it does not do quite what they want: it finds some non-ISO practices, but not all—only those for which ISO C requires a diagnostic, and some others for which diagnostics have been added.

A feature to report any failure to conform to ISO C might be useful in some instances, but would require considerable additional work and would be quite different from -Wpedantic. We don’t have plans to support such a feature in the near future.

Where the standard specified with -std represents a GNU extended dialect of C, such as ‘gnu90’ or ‘gnu99’, there is a corresponding base standard, the version of ISO C on which the GNU extended dialect is based. Warnings from -Wpedantic are given where they are required by the base standard. (It does not make sense for such warnings to be given only for features not in the specified GNU C dialect, since by definition the GNU dialects of C include all features the compiler supports with the given option, and there would be nothing to warn about.)

Give an error whenever the base standard (see -Wpedantic) requires a diagnostic, in some cases where there is undefined behavior at compile-time and in some other cases that do not prevent compilation of programs that are valid according to the standard. This is not equivalent to -Werror=pedantic, since there are errors enabled by this option and not enabled by the latter and vice versa.
This enables all the warnings about constructions that some users consider questionable, and that are easy to avoid (or modify to prevent the warning), even in conjunction with macros. This also enables some language-specific warnings described in C++ Dialect Options and Objective-C and Objective-C++ Dialect Options.-Wall turns on the following warning flags:

          -Warray-bounds=1 (only with -O2)  
          -Wc++11-compat  -Wc++14-compat
          -Wenum-compare (in C/ObjC; this is on by default in C++) 
          -Wimplicit-int (C and Objective-C only) 
          -Wimplicit-function-declaration (C and Objective-C only) 
          -Wmain (only for C/ObjC and unless -ffreestanding)  
          -Wmissing-braces (only for C/ObjC) 
          -Wsign-compare (only in C++)  

Note that some warning flags are not implied by -Wall. Some of them warn about constructions that users generally do not consider questionable, but which occasionally you might wish to check for; others warn about constructions that are necessary or hard to avoid in some cases, and there is no simple way to modify the code to suppress the warning. Some of them are enabled by -Wextra but many of them must be enabled individually.

This enables some extra warning flags that are not enabled by -Wall. (This option used to be called -W. The older name is still supported, but the newer name is more descriptive.)

          -Wmissing-parameter-type (C only)  
          -Wold-style-declaration (C only)  
          -Wunused-parameter (only with -Wunused or -Wall) 
          -Wunused-but-set-parameter (only with -Wunused or -Wall)  

The option -Wextra also prints warning messages for the following cases:

  • A pointer is compared against integer zero with <, <=, >, or >=.
  • (C++ only) An enumerator and a non-enumerator both appear in a conditional expression.
  • (C++ only) Ambiguous virtual bases.
  • (C++ only) Subscripting an array that has been declared register.
  • (C++ only) Taking the address of a variable that has been declared register.
  • (C++ only) A base class is not initialized in a derived class’s copy constructor.
Warn if an array subscript has type char. This is a common cause of error, as programmers often forget that this type is signed on some machines. This warning is enabled by -Wall.
Warn whenever a comment-start sequence ‘/*’ appears in a ‘/*’ comment, or whenever a Backslash-Newline appears in a ‘//’ comment. This warning is enabled by -Wall.
Warn if feedback profiles do not match when using the -fprofile-use option. If a source file is changed between compiling with -fprofile-gen and with -fprofile-use, the files with the profile feedback can fail to match the source file and GCC cannot use the profile feedback information. By default, this warning is enabled and is treated as an error. -Wno-coverage-mismatch can be used to disable the warning or -Wno-error=coverage-mismatch can be used to disable the error. Disabling the error for this warning can result in poorly optimized code and is useful only in the case of very minor changes such as bug fixes to an existing code-base. Completely disabling the warning is not recommended.
(C, Objective-C, C++, Objective-C++ and Fortran only)Suppress warning messages emitted by #warning directives.

-Wdouble-promotion (C, C++, Objective-C and Objective-C++ only)
Give a warning when a value of type float is implicitly promoted to double. CPUs with a 32-bit “single-precision” floating-point unit implement float in hardware, but emulatedouble in software. On such a machine, doing computations using double values is much more expensive because of the overhead required for software emulation.It is easy to accidentally do computations with double because floating-point literals are implicitly of type double. For example, in:

          float area(float radius)
             return 3.14159 * radius * radius;

the compiler performs the entire computation with double because the floating-point literal is a double.

Check calls to printf and scanf, etc., to make sure that the arguments supplied have types appropriate to the format string specified, and that the conversions specified in the format string make sense. This includes standard functions, and others specified by format attributes (see Function Attributes), in the printf, scanf, strftime and strfmon (an X/Open extension, not in the C standard) families (or other target-specific families). Which functions are checked without format attributes having been specified depends on the standard version selected, and such checks of functions without the attribute specified are disabled by -ffreestanding or -fno-builtin.The formats are checked against the format features supported by GNU libc version 2.2. These include all ISO C90 and C99 features, as well as features from the Single Unix Specification and some BSD and GNU extensions. Other library implementations may not support all these features; GCC does not support warning about features that go beyond a particular library’s limitations. However, if -Wpedantic is used with -Wformat, warnings are given about format features not in the selected standard version (but not for strfmonformats, since those are not in any version of the C standard). See Options Controlling C Dialect.

Option -Wformat is equivalent to -Wformat=1, and -Wno-format is equivalent to -Wformat=0. Since -Wformat also checks for null format arguments for several functions, -Wformat also implies -Wnonnull. Some aspects of this level of format checking can be disabled by the options: -Wno-format-contains-nul, -Wno-format-extra-args, and -Wno-format-zero-length. -Wformat is enabled by -Wall.
If -Wformat is specified, do not warn about format strings that contain NUL bytes.
If -Wformat is specified, do not warn about excess arguments to a printf or scanf format function. The C standard specifies that such arguments are ignored.Where the unused arguments lie between used arguments that are specified with ‘$’ operand number specifications, normally warnings are still given, since the implementation could not know what type to pass to va_arg to skip the unused arguments. However, in the case of scanf formats, this option suppresses the warning if the unused arguments are all pointers, since the Single Unix Specification says that such unused arguments are allowed.

If -Wformat is specified, do not warn about zero-length formats. The C standard specifies that zero-length formats are allowed.
Enable -Wformat plus additional format checks. Currently equivalent to -Wformat -Wformat-nonliteral -Wformat-security -Wformat-y2k.
If -Wformat is specified, also warn if the format string is not a string literal and so cannot be checked, unless the format function takes its format arguments as a va_list.
If -Wformat is specified, also warn about uses of format functions that represent possible security problems. At present, this warns about calls to printf and scanf functions where the format string is not a string literal and there are no format arguments, as in printf (foo);. This may be a security hole if the format string came from untrusted input and contains ‘%n’. (This is currently a subset of what -Wformat-nonliteral warns about, but in future warnings may be added to -Wformat-security that are not included in -Wformat-nonliteral.)
If -Wformat is specified, also warn if the format string requires an unsigned argument and the argument is signed and vice versa.
If -Wformat is specified, also warn about strftime formats that may yield only a two-digit year.
Warn about passing a null pointer for arguments marked as requiring a non-null value by the nonnull function attribute.Also warns when comparing an argument marked with the nonnull function attribute against null inside the function.

-Wnonnull is included in -Wall and -Wformat. It can be disabled with the -Wno-nonnull option.

Warn if the compiler detects paths that trigger erroneous or undefined behavior due to dereferencing a null pointer. This option is only active when -fdelete-null-pointer-checksis active, which is enabled by optimizations in most targets. The precision of the warnings depends on the optimization options used.
-Winit-self (C, C++, Objective-C and Objective-C++ only)
Warn about uninitialized variables that are initialized with themselves. Note this option can only be used with the -Wuninitialized option.For example, GCC warns about i being uninitialized in the following snippet only when -Winit-self has been specified:

          int f()
            int i = i;
            return i;

This warning is enabled by -Wall in C++.

-Wimplicit-int (C and Objective-C only)
Warn when a declaration does not specify a type. This warning is enabled by -Wall.
-Wimplicit-function-declaration (C and Objective-C only)
Give a warning whenever a function is used before being declared. In C99 mode (-std=c99 or -std=gnu99), this warning is enabled by default and it is made into an error by -pedantic-errors. This warning is also enabled by -Wall.
-Wimplicit (C and Objective-C only)
Same as -Wimplicit-int and -Wimplicit-function-declaration. This warning is enabled by -Wall.
-Wignored-qualifiers (C and C++ only)
Warn if the return type of a function has a type qualifier such as const. For ISO C such a type qualifier has no effect, since the value returned by a function is not an lvalue. For C++, the warning is only emitted for scalar types or void. ISO C prohibits qualified void return types on function definitions, so such return types always receive a warning even without this option.This warning is also enabled by -Wextra.

Warn if the type of main is suspicious. main should be a function with external linkage, returning int, taking either zero arguments, two, or three arguments of appropriate types. This warning is enabled by default in C++ and is enabled by either -Wall or -Wpedantic.
-Wmisleading-indentation (C and C++ only)
Warn when the indentation of the code does not reflect the block structure. Specifically, a warning is issued for if, else, while, and for clauses with a guarded statement that does not use braces, followed by an unguarded statement with the same indentation.This warning is disabled by default.

In the following example, the call to “bar” is misleadingly indented as if it were guarded by the “if” conditional.

            if (some_condition ())
              foo ();
              bar ();  /* Gotcha: this is not guarded by the "if".  */

In the case of mixed tabs and spaces, the warning uses the -ftabstop= option to determine if the statements line up (defaulting to 8).

The warning is not issued for code involving multiline preprocessor logic such as the following example.

            if (flagA)
              foo (0);
            if (flagB)
              foo (1);

The warning is not issued after a #line directive, since this typically indicates autogenerated code, and no assumptions can be made about the layout of the file that the directive references.

Warn if an aggregate or union initializer is not fully bracketed. In the following example, the initializer for a is not fully bracketed, but that for b is fully bracketed. This warning is enabled by -Wall in C.

          int a[2][2] = { 0, 1, 2, 3 };
          int b[2][2] = { { 0, 1 }, { 2, 3 } };

This warning is enabled by -Wall.

-Wmissing-include-dirs (C, C++, Objective-C and Objective-C++ only)
Warn if a user-supplied include directory does not exist.
Warn if parentheses are omitted in certain contexts, such as when there is an assignment in a context where a truth value is expected, or when operators are nested whose precedence people often get confused about.Also warn if a comparison like x<=y<=z appears; this is equivalent to (x<=y ? 1 : 0) <= z, which is a different interpretation from that of ordinary mathematical notation.

Also warn about constructions where there may be confusion to which if statement an else branch belongs. Here is an example of such a case:

            if (a)
              if (b)
                foo ();
              bar ();

In C/C++, every else branch belongs to the innermost possible if statement, which in this example is if (b). This is often not what the programmer expected, as illustrated in the above example by indentation the programmer chose. When there is the potential for this confusion, GCC issues a warning when this flag is specified. To eliminate the warning, add explicit braces around the innermost if statement so there is no way the else can belong to the enclosing if. The resulting code looks like this:

            if (a)
                if (b)
                  foo ();
                  bar ();

Also warn for dangerous uses of the GNU extension to ?: with omitted middle operand. When the condition in the ?: operator is a boolean expression, the omitted value is always 1. Often programmers expect it to be a value computed inside the conditional expression instead.

This warning is enabled by -Wall.

Warn about code that may have undefined semantics because of violations of sequence point rules in the C and C++ standards.The C and C++ standards define the order in which expressions in a C/C++ program are evaluated in terms of sequence points, which represent a partial ordering between the execution of parts of the program: those executed before the sequence point, and those executed after it. These occur after the evaluation of a full expression (one which is not part of a larger expression), after the evaluation of the first operand of a &&, ||, ? : or , (comma) operator, before a function is called (but after the evaluation of its arguments and the expression denoting the called function), and in certain other places. Other than as expressed by the sequence point rules, the order of evaluation of subexpressions of an expression is not specified. All these rules describe only a partial order rather than a total order, since, for example, if two functions are called within one expression with no sequence point between them, the order in which the functions are called is not specified. However, the standards committee have ruled that function calls do not overlap.

It is not specified when between sequence points modifications to the values of objects take effect. Programs whose behavior depends on this have undefined behavior; the C and C++ standards specify that “Between the previous and next sequence point an object shall have its stored value modified at most once by the evaluation of an expression. Furthermore, the prior value shall be read only to determine the value to be stored.”. If a program breaks these rules, the results on any particular implementation are entirely unpredictable.

Examples of code with undefined behavior are a = a++;, a[n] = b[n++] and a[i++] = i;. Some more complicated cases are not diagnosed by this option, and it may give an occasional false positive result, but in general it has been found fairly effective at detecting this sort of problem in programs.

The standard is worded confusingly, therefore there is some debate over the precise meaning of the sequence point rules in subtle cases. Links to discussions of the problem, including proposed formal definitions, may be found on the GCC readings page, at

This warning is enabled by -Wall for C and C++.

Do not warn about returning a pointer (or in C++, a reference) to a variable that goes out of scope after the function returns.
Warn whenever a function is defined with a return type that defaults to int. Also warn about any return statement with no return value in a function whose return type is not void(falling off the end of the function body is considered returning without a value), and about a return statement with an expression in a function whose return type is void.For C++, a function without return type always produces a diagnostic message, even when -Wno-return-type is specified. The only exceptions are main and functions defined in system headers.

This warning is enabled by -Wall.

Warn if shift count is negative. This warning is enabled by default.
Warn if shift count >= width of type. This warning is enabled by default.
Warn if left shifting a negative value. This warning is enabled by -Wextra in C99 and C++11 modes (and newer).
Warn about left shift overflows. This warning is enabled by default in C99 and C++11 modes (and newer).

This is the warning level of -Wshift-overflow and is enabled by default in C99 and C++11 modes (and newer). This warning level does not warn about left-shifting 1 into the sign bit. (However, in C, such an overflow is still rejected in contexts where an integer constant expression is required.)
This warning level also warns about left-shifting 1 into the sign bit, unless C++14 mode is active.
Warn whenever a switch statement has an index of enumerated type and lacks a case for one or more of the named codes of that enumeration. (The presence of a default label prevents this warning.) case labels outside the enumeration range also provoke warnings when this option is used (even if there is a default label). This warning is enabled by -Wall.
Warn whenever a switch statement does not have a default case.
Warn whenever a switch statement has an index of enumerated type and lacks a case for one or more of the named codes of that enumeration. case labels outside the enumeration range also provoke warnings when this option is used. The only difference between -Wswitch and this option is that this option gives a warning about an omitted enumeration code even if there is a default label.
Warn whenever a switch statement has an index of boolean type and the case values are outside the range of a boolean type. It is possible to suppress this warning by casting the controlling expression to a type other than bool. For example:

          switch ((int) (a == 4))

This warning is enabled by default for C and C++ programs.

-Wsync-nand (C and C++ only)
Warn when __sync_fetch_and_nand and __sync_nand_and_fetch built-in functions are used. These functions changed semantics in GCC 4.4.
Warn if any trigraphs are encountered that might change the meaning of the program (trigraphs within comments are not warned about). This warning is enabled by -Wall.
Warn whenever a function parameter is assigned to, but otherwise unused (aside from its declaration).To suppress this warning use the unused attribute (see Variable Attributes).

This warning is also enabled by -Wunused together with -Wextra.

Warn whenever a local variable is assigned to, but otherwise unused (aside from its declaration). This warning is enabled by -Wall.To suppress this warning use the unused attribute (see Variable Attributes).

This warning is also enabled by -Wunused, which is enabled by -Wall.

Warn whenever a static function is declared but not defined or a non-inline static function is unused. This warning is enabled by -Wall.
Warn whenever a label is declared but not used. This warning is enabled by -Wall.To suppress this warning use the unused attribute (see Variable Attributes).

-Wunused-local-typedefs (C, Objective-C, C++ and Objective-C++ only)
Warn when a typedef locally defined in a function is not used. This warning is enabled by -Wall.
Warn whenever a function parameter is unused aside from its declaration.To suppress this warning use the unused attribute (see Variable Attributes).

Do not warn if a caller of a function marked with attribute warn_unused_result (see Function Attributes) does not use its return value. The default is -Wunused-result.
Warn whenever a local or static variable is unused aside from its declaration. This option implies -Wunused-const-variable for C, but not for C++. This warning is enabled by -Wall.To suppress this warning use the unused attribute (see Variable Attributes).

Warn whenever a constant static variable is unused aside from its declaration. This warning is enabled by -Wunused-variable for C, but not for C++. In C++ this is normally not an error since const variables take the place of #defines in C++.To suppress this warning use the unused attribute (see Variable Attributes).

Warn whenever a statement computes a result that is explicitly not used. To suppress this warning cast the unused expression to void. This includes an expression-statement or the left-hand side of a comma expression that contains no side effects. For example, an expression such as x[i,j] causes a warning, while x[(void)i,j] does not.This warning is enabled by -Wall.

All the above -Wunused options combined.In order to get a warning about an unused function parameter, you must either specify -Wextra -Wunused (note that -Wall implies -Wunused), or separately specify -Wunused-parameter.

Warn if an automatic variable is used without first being initialized or if a variable may be clobbered by a setjmp call. In C++, warn if a non-static reference or non-static constmember appears in a class without constructors.If you want to warn about code that uses the uninitialized value of the variable in its own initializer, use the -Winit-self option.

These warnings occur for individual uninitialized or clobbered elements of structure, union or array variables as well as for variables that are uninitialized or clobbered as a whole. They do not occur for variables or elements declared volatile. Because these warnings depend on optimization, the exact variables or elements for which there are warnings depends on the precise optimization options and version of GCC used.

Note that there may be no warning about a variable that is used only to compute a value that itself is never used, because such computations may be deleted by data flow analysis before the warnings are printed.

For an automatic variable, if there exists a path from the function entry to a use of the variable that is initialized, but there exist some other paths for which the variable is not initialized, the compiler emits a warning if it cannot prove the uninitialized paths are not executed at run time. These warnings are made optional because GCC is not smart enough to see all the reasons why the code might be correct in spite of appearing to have an error. Here is one example of how this can happen:

            int x;
            switch (y)
              case 1: x = 1;
              case 2: x = 4;
              case 3: x = 5;
            foo (x);

If the value of y is always 1, 2 or 3, then x is always initialized, but GCC doesn’t know this. To suppress the warning, you need to provide a default case with assert(0) or similar code.

This option also warns when a non-volatile automatic variable might be changed by a call to longjmp. These warnings as well are possible only in optimizing compilation.

The compiler sees only the calls to setjmp. It cannot know where longjmp will be called; in fact, a signal handler could call it at any point in the code. As a result, you may get a warning even when there is in fact no problem because longjmp cannot in fact be called at the place that would cause a problem.

Some spurious warnings can be avoided if you declare all the functions you use that never return as noreturn. See Function Attributes.

This warning is enabled by -Wall or -Wextra.

Warn when a #pragma directive is encountered that is not understood by GCC. If this command-line option is used, warnings are even issued for unknown pragmas in system header files. This is not the case if the warnings are only enabled by the -Wall command-line option.
Do not warn about misuses of pragmas, such as incorrect parameters, invalid syntax, or conflicts between pragmas. See also -Wunknown-pragmas.
This option is only active when -fstrict-aliasing is active. It warns about code that might break the strict aliasing rules that the compiler is using for optimization. The warning does not catch all cases, but does attempt to catch the more common pitfalls. It is included in -Wall. It is equivalent to -Wstrict-aliasing=3
This option is only active when -fstrict-aliasing is active. It warns about code that might break the strict aliasing rules that the compiler is using for optimization. Higher levels correspond to higher accuracy (fewer false positives). Higher levels also correspond to more effort, similar to the way -O works. -Wstrict-aliasing is equivalent to -Wstrict-aliasing=3.Level 1: Most aggressive, quick, least accurate. Possibly useful when higher levels do not warn but -fstrict-aliasing still breaks the code, as it has very few false negatives. However, it has many false positives. Warns for all pointer conversions between possibly incompatible types, even if never dereferenced. Runs in the front end only.

Level 2: Aggressive, quick, not too precise. May still have many false positives (not as many as level 1 though), and few false negatives (but possibly more than level 1). Unlike level 1, it only warns when an address is taken. Warns about incomplete types. Runs in the front end only.

Level 3 (default for -Wstrict-aliasing): Should have very few false positives and few false negatives. Slightly slower than levels 1 or 2 when optimization is enabled. Takes care of the common pun+dereference pattern in the front end: *(int*)&some_float. If optimization is enabled, it also runs in the back end, where it deals with multiple statement cases using flow-sensitive points-to information. Only warns when the converted pointer is dereferenced. Does not warn about incomplete types.

This option is only active when -fstrict-overflow is active. It warns about cases where the compiler optimizes based on the assumption that signed overflow does not occur. Note that it does not warn about all cases where the code might overflow: it only warns about cases where the compiler implements some optimization. Thus this warning depends on the optimization level.An optimization that assumes that signed overflow does not occur is perfectly safe if the values of the variables involved are such that overflow never does, in fact, occur. Therefore this warning can easily give a false positive: a warning about code that is not actually a problem. To help focus on important issues, several warning levels are defined. No warnings are issued for the use of undefined signed overflow when estimating how many iterations a loop requires, in particular when determining whether a loop will be executed at all.

Warn about cases that are both questionable and easy to avoid. For example, with -fstrict-overflow, the compiler simplifies x + 1 > x to 1. This level of -Wstrict-overflow is enabled by -Wall; higher levels are not, and must be explicitly requested.
Also warn about other cases where a comparison is simplified to a constant. For example: abs (x) >= 0. This can only be simplified when -fstrict-overflow is in effect, because abs (INT_MIN) overflows to INT_MIN, which is less than zero. -Wstrict-overflow (with no level) is the same as -Wstrict-overflow=2.
Also warn about other cases where a comparison is simplified. For example: x + 1 > 1 is simplified to x > 0.
Also warn about other simplifications not covered by the above cases. For example: (x * 10) / 5 is simplified to x * 2.
Also warn about cases where the compiler reduces the magnitude of a constant involved in a comparison. For example: x + 2 > y is simplified to x + 1 >= y. This is reported only at the highest warning level because this simplification applies to many comparisons, so this warning level gives a very large number of false positives.
Warn for cases where adding an attribute may be beneficial. The attributes currently supported are listed below.

Warn about functions that might be candidates for attributes pure, const or noreturn. The compiler only warns for functions visible in other compilation units or (in the case ofpure and const) if it cannot prove that the function returns normally. A function returns normally if it doesn’t contain an infinite loop or return abnormally by throwing, callingabort or trapping. This analysis requires option -fipa-pure-const, which is enabled by default at -O and higher. Higher optimization levels improve the accuracy of the analysis.
Warn about function pointers that might be candidates for format attributes. Note these are only possible candidates, not absolute ones. GCC guesses that function pointers withformat attributes that are used in assignment, initialization, parameter passing or return statements should have a corresponding format attribute in the resulting type. I.e. the left-hand side of the assignment or initialization, the type of the parameter variable, or the return type of the containing function respectively should also have a format attribute to avoid the warning.GCC also warns about function definitions that might be candidates for format attributes. Again, these are only possible candidates. GCC guesses that format attributes might be appropriate for any function that calls a function like vprintf or vscanf, but this might not always be the case, and some functions for which format attributes are appropriate may not be detected.

Warn about types with virtual methods where code quality would be improved if the type were declared with the C++11 final specifier, or, if possible, declared in an anonymous namespace. This allows GCC to more aggressively devirtualize the polymorphic calls. This warning is more effective with link time optimization, where the information about the class hierarchy graph is more complete.
Warn about virtual methods where code quality would be improved if the method were declared with the C++11 final specifier, or, if possible, its type were declared in an anonymous namespace or with the final specifier. This warning is more effective with link time optimization, where the information about the class hierarchy graph is more complete. It is recommended to first consider suggestions of -Wsuggest-final-types and then rebuild with new annotations.
Warn about overriding virtual functions that are not marked with the override keyword.
This option is only active when -ftree-vrp is active (default for -O2 and above). It warns about subscripts to arrays that are always out of bounds. This warning is enabled by -Wall.

This is the warning level of -Warray-bounds and is enabled by -Wall; higher levels are not, and must be explicitly requested.
This warning level also warns about out of bounds access for arrays at the end of a struct and for arrays accessed through pointers. This warning level may give a larger number of false positives and is deactivated by default.
Warn about boolean expression compared with an integer value different from true/false. For instance, the following comparison is always false:

          int n = 5;
          if ((n > 1) == 2) { ... }

This warning is enabled by -Wall.

Warn about duplicated conditions in an if-else-if chain. For instance, warn for the following code:

          if (p->q != NULL) { ... }
          else if (p->q != NULL) { ... }

This warning is enabled by -Wall.

Warn when the ‘__builtin_frame_address’ or ‘__builtin_return_address’ is called with an argument greater than 0. Such calls may return indeterminate values or crash the program. The warning is included in -Wall.
-Wno-discarded-qualifiers (C and Objective-C only)
Do not warn if type qualifiers on pointers are being discarded. Typically, the compiler warns if a const char * variable is passed to a function that takes a char * parameter. This option can be used to suppress such a warning.
-Wno-discarded-array-qualifiers (C and Objective-C only)
Do not warn if type qualifiers on arrays which are pointer targets are being discarded. Typically, the compiler warns if a const int (*)[] variable is passed to a function that takes aint (*)[] parameter. This option can be used to suppress such a warning.
-Wno-incompatible-pointer-types (C and Objective-C only)
Do not warn when there is a conversion between pointers that have incompatible types. This warning is for cases not covered by -Wno-pointer-sign, which warns for pointer argument passing or assignment with different signedness.
-Wno-int-conversion (C and Objective-C only)
Do not warn about incompatible integer to pointer and pointer to integer conversions. This warning is about implicit conversions; for explicit conversions the warnings -Wno-int-to-pointer-cast and -Wno-pointer-to-int-cast may be used.
Do not warn about compile-time integer division by zero. Floating-point division by zero is not warned about, as it can be a legitimate way of obtaining infinities and NaNs.
Print warning messages for constructs found in system header files. Warnings from system headers are normally suppressed, on the assumption that they usually do not indicate real problems and would only make the compiler output harder to read. Using this command-line option tells GCC to emit warnings from system headers as if they occurred in user code. However, note that using -Wall in conjunction with this option does not warn about unknown pragmas in system headers—for that, -Wunknown-pragmas must also be used.
Warn if a self-comparison always evaluates to true or false. This warning detects various mistakes such as:

          int i = 1;
          if (i > i) { ... }

This warning is enabled by -Wall.

Warn about trampolines generated for pointers to nested functions. A trampoline is a small piece of data or code that is created at run time on the stack when the address of a nested function is taken, and is used to call the nested function indirectly. For some targets, it is made up of data only and thus requires no special treatment. But, for most targets, it is made up of code and thus requires the stack to be made executable in order for the program to work properly.
Warn if floating-point values are used in equality comparisons.The idea behind this is that sometimes it is convenient (for the programmer) to consider floating-point values as approximations to infinitely precise real numbers. If you are doing this, then you need to compute (by analyzing the code, or in some other way) the maximum or likely maximum error that the computation introduces, and allow for it when performing comparisons (and when producing output, but that’s a different problem). In particular, instead of testing for equality, you should check to see whether the two values have ranges that overlap; and this is done with the relational operators, so equality comparisons are probably mistaken.

-Wtraditional (C and Objective-C only)
Warn about certain constructs that behave differently in traditional and ISO C. Also warn about ISO C constructs that have no traditional C equivalent, and/or problematic constructs that should be avoided.

  • Macro parameters that appear within string literals in the macro body. In traditional C macro replacement takes place within string literals, but in ISO C it does not.
  • In traditional C, some preprocessor directives did not exist. Traditional preprocessors only considered a line to be a directive if the ‘#’ appeared in column 1 on the line. Therefore -Wtraditional warns about directives that traditional C understands but ignores because the ‘#’ does not appear as the first character on the line. It also suggests you hide directives like #pragma not understood by traditional C by indenting them. Some traditional implementations do not recognize #elif, so this option suggests avoiding it altogether.
  • A function-like macro that appears without arguments.
  • The unary plus operator.
  • The ‘U’ integer constant suffix, or the ‘F’ or ‘L’ floating-point constant suffixes. (Traditional C does support the ‘L’ suffix on integer constants.) Note, these suffixes appear in macros defined in the system headers of most modern systems, e.g. the ‘_MIN’/‘_MAX’ macros in <limits.h>. Use of these macros in user code might normally lead to spurious warnings, however GCC’s integrated preprocessor has enough context to avoid warning in these cases.
  • A function declared external in one block and then used after the end of the block.
  • A switch statement has an operand of type long.
  • A non-static function declaration follows a static one. This construct is not accepted by some traditional C compilers.
  • The ISO type of an integer constant has a different width or signedness from its traditional type. This warning is only issued if the base of the constant is ten. I.e. hexadecimal or octal values, which typically represent bit patterns, are not warned about.
  • Usage of ISO string concatenation is detected.
  • Initialization of automatic aggregates.
  • Identifier conflicts with labels. Traditional C lacks a separate namespace for labels.
  • Initialization of unions. If the initializer is zero, the warning is omitted. This is done under the assumption that the zero initializer in user code appears conditioned on e.g.__STDC__ to avoid missing initializer warnings and relies on default initialization to zero in the traditional C case.
  • Conversions by prototypes between fixed/floating-point values and vice versa. The absence of these prototypes when compiling with traditional C causes serious problems. This is a subset of the possible conversion warnings; for the full set use -Wtraditional-conversion.
  • Use of ISO C style function definitions. This warning intentionally is not issued for prototype declarations or variadic functions because these ISO C features appear in your code when using libiberty’s traditional C compatibility macros, PARAMS and VPARAMS. This warning is also bypassed for nested functions because that feature is already a GCC extension and thus not relevant to traditional C compatibility.
-Wtraditional-conversion (C and Objective-C only)
Warn if a prototype causes a type conversion that is different from what would happen to the same argument in the absence of a prototype. This includes conversions of fixed point to floating and vice versa, and conversions changing the width or signedness of a fixed-point argument except when the same as the default promotion.
-Wdeclaration-after-statement (C and Objective-C only)
Warn when a declaration is found after a statement in a block. This construct, known from C++, was introduced with ISO C99 and is by default allowed in GCC. It is not supported by ISO C90. See Mixed Declarations.
Warn if an undefined identifier is evaluated in an #if directive.
Do not warn whenever an #else or an #endif are followed by text.
Warn whenever a local variable or type declaration shadows another variable, parameter, type, class member (in C++), or instance variable (in Objective-C) or whenever a built-in function is shadowed. Note that in C++, the compiler warns if a local variable shadows an explicit typedef, but not if it shadows a struct/class/enum.
-Wno-shadow-ivar (Objective-C only)
Do not warn whenever a local variable shadows an instance variable in an Objective-C method.
Warn whenever an object of larger than len bytes is defined.
Warn if the size of a function frame is larger than len bytes. The computation done to determine the stack frame size is approximate and not conservative. The actual requirements may be somewhat greater than len even if you do not get a warning. In addition, any space allocated via alloca, variable-length arrays, or related constructs is not included by the compiler when determining whether or not to issue a warning.
Do not warn when attempting to free an object that was not allocated on the heap.
Warn if the stack usage of a function might be larger than len bytes. The computation done to determine the stack usage is conservative. Any space allocated via alloca, variable-length arrays, or related constructs is included by the compiler when determining whether or not to issue a warning.The message is in keeping with the output of -fstack-usage.

  • If the stack usage is fully static but exceeds the specified amount, it’s:
                     warning: stack usage is 1120 bytes
  • If the stack usage is (partly) dynamic but bounded, it’s:
                     warning: stack usage might be 1648 bytes
  • If the stack usage is (partly) dynamic and not bounded, it’s:
                     warning: stack usage might be unbounded
Warn if the loop cannot be optimized because the compiler cannot assume anything on the bounds of the loop indices. With -funsafe-loop-optimizations warn if the compiler makes such assumptions.
-Wno-pedantic-ms-format (MinGW targets only)
When used in combination with -Wformat and -pedantic without GNU extensions, this option disables the warnings about non-ISO printf / scanf format width specifiers I32, I64, and I used on Windows targets, which depend on the MS runtime.
Warn about placement new expressions with undefined behavior, such as constructing an object in a buffer that is smaller than the type of the object.
Warn about anything that depends on the “size of” a function type or of void. GNU C assigns these types a size of 1, for convenience in calculations with void * pointers and pointers to functions. In C++, warn also when an arithmetic operation involves NULL. This warning is also enabled by -Wpedantic.
Warn if a comparison is always true or always false due to the limited range of the data type, but do not warn for constant expressions. For example, warn if an unsigned variable is compared against zero with < or >=. This warning is also enabled by -Wextra.
-Wbad-function-cast (C and Objective-C only)
Warn when a function call is cast to a non-matching type. For example, warn if a call to a function returning an integer type is cast to a pointer type.
-Wc90-c99-compat (C and Objective-C only)
Warn about features not present in ISO C90, but present in ISO C99. For instance, warn about use of variable length arrays, long long type, bool type, compound literals, designated initializers, and so on. This option is independent of the standards mode. Warnings are disabled in the expression that follows __extension__.
-Wc99-c11-compat (C and Objective-C only)
Warn about features not present in ISO C99, but present in ISO C11. For instance, warn about use of anonymous structures and unions, _Atomic type qualifier, _Thread_localstorage-class specifier, _Alignas specifier, Alignof operator, _Generic keyword, and so on. This option is independent of the standards mode. Warnings are disabled in the expression that follows __extension__.
-Wc++-compat (C and Objective-C only)
Warn about ISO C constructs that are outside of the common subset of ISO C and ISO C++, e.g. request for implicit conversion from void * to a pointer to non-void type.
-Wc++11-compat (C++ and Objective-C++ only)
Warn about C++ constructs whose meaning differs between ISO C++ 1998 and ISO C++ 2011, e.g., identifiers in ISO C++ 1998 that are keywords in ISO C++ 2011. This warning turns on -Wnarrowing and is enabled by -Wall.
-Wc++14-compat (C++ and Objective-C++ only)
Warn about C++ constructs whose meaning differs between ISO C++ 2011 and ISO C++ 2014. This warning is enabled by -Wall.
Warn whenever a pointer is cast so as to remove a type qualifier from the target type. For example, warn if a const char * is cast to an ordinary char *.Also warn when making a cast that introduces a type qualifier in an unsafe way. For example, casting char ** to const char ** is unsafe, as in this example:

            /* p is char ** value.  */
            const char **q = (const char **) p;
            /* Assignment of readonly string to const char * is OK.  */
            *q = "string";
            /* Now char** pointer points to read-only memory.  */
            **p = 'b';
Warn whenever a pointer is cast such that the required alignment of the target is increased. For example, warn if a char * is cast to an int * on machines where integers can only be accessed at two- or four-byte boundaries.
When compiling C, give string constants the type const char[length] so that copying the address of one into a non-const char * pointer produces a warning. These warnings help you find at compile time code that can try to write into a string constant, but only if you have been very careful about using const in declarations and prototypes. Otherwise, it is just a nuisance. This is why we did not make -Wall request these warnings.When compiling C++, warn about the deprecated conversion from string literals to char *. This warning is enabled by default for C++ programs.

Warn for variables that might be changed by longjmp or vfork. This warning is also enabled by -Wextra.
-Wconditionally-supported (C++ and Objective-C++ only)
Warn for conditionally-supported (C++11 [intro.defs]) constructs.
Warn for implicit conversions that may alter a value. This includes conversions between real and integer, like abs (x) when x is double; conversions between signed and unsigned, like unsigned ui = -1; and conversions to smaller types, like sqrtf (M_PI). Do not warn for explicit casts like abs ((int) x) and ui = (unsigned) -1, or if the value is not changed by the conversion like in abs (2.0). Warnings about conversions between signed and unsigned integers can be disabled by using -Wno-sign-conversion.For C++, also warn for confusing overload resolution for user-defined conversions; and conversions that never use a type conversion operator: conversions to void, the same type, a base class or a reference to them. Warnings about conversions between signed and unsigned integers are disabled by default in C++ unless -Wsign-conversion is explicitly enabled.

-Wno-conversion-null (C++ and Objective-C++ only)
Do not warn for conversions between NULL and non-pointer types. -Wconversion-null is enabled by default.
-Wzero-as-null-pointer-constant (C++ and Objective-C++ only)
Warn when a literal ‘0’ is used as null pointer constant. This can be useful to facilitate the conversion to nullptr in C++11.
-Wsubobject-linkage (C++ and Objective-C++ only)
Warn if a class type has a base or a field whose type uses the anonymous namespace or depends on a type with no linkage. If a type A depends on a type B with no or internal linkage, defining it in multiple translation units would be an ODR violation because the meaning of B is different in each translation unit. If A only appears in a single translation unit, the best way to silence the warning is to give it internal linkage by putting it in an anonymous namespace as well. The compiler doesn’t give this warning for types defined in the main .C file, as those are unlikely to have multiple definitions. -Wsubobject-linkage is enabled by default.
Warn when macros __TIME__, __DATE__ or __TIMESTAMP__ are encountered as they might prevent bit-wise-identical reproducible compilations.
-Wdelete-incomplete (C++ and Objective-C++ only)
Warn when deleting a pointer to incomplete type, which may cause undefined behavior at runtime. This warning is enabled by default.
-Wuseless-cast (C++ and Objective-C++ only)
Warn when an expression is casted to its own type.
Warn if an empty body occurs in an if, else or do while statement. This warning is also enabled by -Wextra.
Warn about a comparison between values of different enumerated types. In C++ enumeral mismatches in conditional expressions are also diagnosed and the warning is enabled by default. In C this warning is enabled by -Wall.
-Wjump-misses-init (C, Objective-C only)
Warn if a goto statement or a switch statement jumps forward across the initialization of a variable, or jumps backward to a label after the variable has been initialized. This only warns about variables that are initialized when they are declared. This warning is only supported for C and Objective-C; in C++ this sort of branch is an error in any case.-Wjump-misses-init is included in -Wc++-compat. It can be disabled with the -Wno-jump-misses-init option.

Warn when a comparison between signed and unsigned values could produce an incorrect result when the signed value is converted to unsigned. This warning is also enabled by -Wextra; to get the other warnings of -Wextra without this warning, use -Wextra -Wno-sign-compare.
Warn for implicit conversions that may change the sign of an integer value, like assigning a signed integer expression to an unsigned integer variable. An explicit cast silences the warning. In C, this option is enabled also by -Wconversion.
Warn for implicit conversions that reduce the precision of a real value. This includes conversions from real to integer, and from higher precision real to lower precision real values. This option is also enabled by -Wconversion.
Do not warn on suspicious constructs involving reverse scalar storage order.
-Wsized-deallocation (C++ and Objective-C++ only)
Warn about a definition of an unsized deallocation function

          void operator delete (void *) noexcept;
          void operator delete[] (void *) noexcept;

without a definition of the corresponding sized deallocation function

          void operator delete (void *, std::size_t) noexcept;
          void operator delete[] (void *, std::size_t) noexcept;

or vice versa. Enabled by -Wextra along with -fsized-deallocation.

Warn for suspicious length parameters to certain string and memory built-in functions if the argument uses sizeof. This warning warns e.g. about memset (ptr, 0, sizeof (ptr)); if ptr is not an array, but a pointer, and suggests a possible fix, or about memcpy (&foo, ptr, sizeof (&foo));. This warning is enabled by -Wall.
Warn when the sizeof operator is applied to a parameter that is declared as an array in a function definition. This warning is enabled by default for C and C++ programs.
Warn for suspicious calls to the memset built-in function, if the second argument is not zero and the third argument is zero. This warns e.g. about memset (buf, sizeof buf, 0)where most probably memset (buf, 0, sizeof buf) was meant instead. The diagnostics is only emitted if the third argument is literal zero. If it is some expression that is folded to zero, a cast of zero to some type, etc., it is far less likely that the user has mistakenly exchanged the arguments and no warning is emitted. This warning is enabled by -Wall.
Warn about suspicious uses of memory addresses. These include using the address of a function in a conditional expression, such as void func(void); if (func), and comparisons against the memory address of a string literal, such as if (x == "abc"). Such uses typically indicate a programmer error: the address of a function always evaluates to true, so their use in a conditional usually indicate that the programmer forgot the parentheses in a function call; and comparisons against string literals result in unspecified behavior and are not portable in C, so they usually indicate that the programmer intended to use strcmp. This warning is enabled by -Wall.
Warn about suspicious uses of logical operators in expressions. This includes using logical operators in contexts where a bit-wise operator is likely to be expected. Also warns when the operands of a logical operator are the same:

          extern int a;
          if (a < 0 && a < 0) { ... }
Warn about logical not used on the left hand side operand of a comparison. This option does not warn if the RHS operand is of a boolean type. Its purpose is to detect suspicious code like the following:

          int a;
          if (!a > 1) { ... }

It is possible to suppress the warning by wrapping the LHS into parentheses:

          if ((!a) > 1) { ... }

This warning is enabled by -Wall.

Warn if any functions that return structures or unions are defined or called. (In languages where you can return an array, this also elicits a warning.)
Warn if in a loop with constant number of iterations the compiler detects undefined behavior in some statement during one or more of the iterations.
Do not warn if an unexpected __attribute__ is used, such as unrecognized attributes, function attributes applied to variables, etc. This does not stop errors for incorrect use of supported attributes.
Do not warn if certain built-in macros are redefined. This suppresses warnings for redefinition of __TIMESTAMP__, __TIME__, __DATE__, __FILE__, and __BASE_FILE__.
-Wstrict-prototypes (C and Objective-C only)
Warn if a function is declared or defined without specifying the argument types. (An old-style function definition is permitted without a warning if preceded by a declaration that specifies the argument types.)
-Wold-style-declaration (C and Objective-C only)
Warn for obsolescent usages, according to the C Standard, in a declaration. For example, warn if storage-class specifiers like static are not the first things in a declaration. This warning is also enabled by -Wextra.
-Wold-style-definition (C and Objective-C only)
Warn if an old-style function definition is used. A warning is given even if there is a previous prototype.
-Wmissing-parameter-type (C and Objective-C only)
A function parameter is declared without a type specifier in K&R-style functions:

          void foo(bar) { }

This warning is also enabled by -Wextra.

-Wmissing-prototypes (C and Objective-C only)
Warn if a global function is defined without a previous prototype declaration. This warning is issued even if the definition itself provides a prototype. Use this option to detect global functions that do not have a matching prototype declaration in a header file. This option is not valid for C++ because all function declarations provide prototypes and a non-matching declaration declares an overload rather than conflict with an earlier declaration. Use -Wmissing-declarations to detect missing declarations in C++.
Warn if a global function is defined without a previous declaration. Do so even if the definition itself provides a prototype. Use this option to detect global functions that are not declared in header files. In C, no warnings are issued for functions with previous non-prototype declarations; use -Wmissing-prototypes to detect missing prototypes. In C++, no warnings are issued for function templates, or for inline functions, or for functions in anonymous namespaces.
Warn if a structure’s initializer has some fields missing. For example, the following code causes such a warning, because x.h is implicitly zero:

          struct s { int f, g, h; };
          struct s x = { 3, 4 };

This option does not warn about designated initializers, so the following modification does not trigger a warning:

          struct s { int f, g, h; };
          struct s x = { .f = 3, .g = 4 };

In C++ this option does not warn either about the empty { } initializer, for example:

          struct s { int f, g, h; };
          s x = { };

This warning is included in -Wextra. To get other -Wextra warnings without this one, use -Wextra -Wno-missing-field-initializers.

Do not warn if a multicharacter constant (‘‘FOOF’’) is used. Usually they indicate a typo in the user’s code, as they have implementation-defined values, and should not be used in portable code.
In ISO C and ISO C++, two identifiers are different if they are different sequences of characters. However, sometimes when characters outside the basic ASCII character set are used, you can have two different character sequences that look the same. To avoid confusion, the ISO 10646 standard sets out some normalization rules which when applied ensure that two sequences that look the same are turned into the same sequence. GCC can warn you if you are using identifiers that have not been normalized; this option controls that warning.There are four levels of warning supported by GCC. The default is -Wnormalized=nfc, which warns about any identifier that is not in the ISO 10646 “C” normalized form, NFC. NFC is the recommended form for most uses. It is equivalent to -Wnormalized.

Unfortunately, there are some characters allowed in identifiers by ISO C and ISO C++ that, when turned into NFC, are not allowed in identifiers. That is, there’s no way to use these symbols in portable ISO C or C++ and have all your identifiers in NFC. -Wnormalized=id suppresses the warning for these characters. It is hoped that future versions of the standards involved will correct this, which is why this option is not the default.

You can switch the warning off for all characters by writing -Wnormalized=none or -Wno-normalized. You should only do this if you are using some other normalization scheme (like “D”), because otherwise you can easily create bugs that are literally impossible to see.

Some characters in ISO 10646 have distinct meanings but look identical in some fonts or display methodologies, especially once formatting has been applied. For instance \u207F, “SUPERSCRIPT LATIN SMALL LETTER N”, displays just like a regular n that has been placed in a superscript. ISO 10646 defines the NFKC normalization scheme to convert all these into a standard form as well, and GCC warns if your code is not in NFKC if you use -Wnormalized=nfkc. This warning is comparable to warning about every identifier that contains the letter O because it might be confused with the digit 0, and so is not the default, but may be useful as a local coding convention if the programming environment cannot be fixed to display these characters distinctly.

Do not warn about usage of deprecated features. See Deprecated Features.
Do not warn about uses of functions (see Function Attributes), variables (see Variable Attributes), and types (see Type Attributes) marked as deprecated by using the deprecatedattribute.
Do not warn about compile-time overflow in constant expressions.
Warn about One Definition Rule violations during link-time optimization. Requires -flto-odr-type-merging to be enabled. Enabled by default.
Warn if the vectorizer cost model overrides the OpenMP or the Cilk Plus simd directive set by user. The -fsimd-cost-model=unlimited option can be used to relax the cost model.
-Woverride-init (C and Objective-C only)
Warn if an initialized field without side effects is overridden when using designated initializers (see Designated Initializers).This warning is included in -Wextra. To get other -Wextra warnings without this one, use -Wextra -Wno-override-init.

-Woverride-init-side-effects (C and Objective-C only)
Warn if an initialized field with side effects is overridden when using designated initializers (see Designated Initializers). This warning is enabled by default.
Warn if a structure is given the packed attribute, but the packed attribute has no effect on the layout or size of the structure. Such structures may be mis-aligned for little benefit. For instance, in this code, the variable f.x in struct bar is misaligned even though struct bar does not itself have the packed attribute:

          struct foo {
            int x;
            char a, b, c, d;
          } __attribute__((packed));
          struct bar {
            char z;
            struct foo f;
The 4.1, 4.2 and 4.3 series of GCC ignore the packed attribute on bit-fields of type char. This has been fixed in GCC 4.4 but the change can lead to differences in the structure layout. GCC informs you when the offset of such a field has changed in GCC 4.4. For example there is no longer a 4-bit padding between field a and b in this structure:

          struct foo
            char a:4;
            char b:8;
          } __attribute__ ((packed));

This warning is enabled by default. Use -Wno-packed-bitfield-compat to disable this warning.

Warn if padding is included in a structure, either to align an element of the structure or to align the whole structure. Sometimes when this happens it is possible to rearrange the fields of the structure to reduce the padding and so make the structure smaller.
Warn if anything is declared more than once in the same scope, even in cases where multiple declaration is valid and changes nothing.
-Wnested-externs (C and Objective-C only)
Warn if an extern declaration is encountered within a function.
Suppress warnings about use of C++11 inheriting constructors when the base class inherited from has a C variadic constructor; the warning is on by default because the ellipsis is not inherited.
Warn if a function that is declared as inline cannot be inlined. Even with this option, the compiler does not warn about failures to inline functions declared in system headers.The compiler uses a variety of heuristics to determine whether or not to inline a function. For example, the compiler takes into account the size of the function being inlined and the amount of inlining that has already been done in the current function. Therefore, seemingly insignificant changes in the source program can cause the warnings produced by -Winlineto appear or disappear.

-Wno-invalid-offsetof (C++ and Objective-C++ only)
Suppress warnings from applying the offsetof macro to a non-POD type. According to the 2014 ISO C++ standard, applying offsetof to a non-standard-layout type is undefined. In existing C++ implementations, however, offsetof typically gives meaningful results. This flag is for users who are aware that they are writing nonportable code and who have deliberately chosen to ignore the warning about it.The restrictions on offsetof may be relaxed in a future version of the C++ standard.

Suppress warnings from casts to pointer type of an integer of a different size. In C++, casting to a pointer type of smaller size is an error. Wint-to-pointer-cast is enabled by default.
-Wno-pointer-to-int-cast (C and Objective-C only)
Suppress warnings from casts from a pointer to an integer type of a different size.
Warn if a precompiled header (see Precompiled Headers) is found in the search path but can’t be used.
Warn if long long type is used. This is enabled by either -Wpedantic or -Wtraditional in ISO C90 and C++98 modes. To inhibit the warning messages, use -Wno-long-long.
Warn if variadic macros are used in ISO C90 mode, or if the GNU alternate syntax is used in ISO C99 mode. This is enabled by either -Wpedantic or -Wtraditional. To inhibit the warning messages, use -Wno-variadic-macros.
Warn upon questionable usage of the macros used to handle variable arguments like va_start. This is default. To inhibit the warning messages, use -Wno-varargs.
Warn if vector operation is not implemented via SIMD capabilities of the architecture. Mainly useful for the performance tuning. Vector operation can be implemented piecewise, which means that the scalar operation is performed on every vector element; in parallel, which means that the vector operation is implemented using scalars of wider type, which normally is more performance efficient; and as a single scalar, which means that vector fits into a scalar type.
Suppress warnings about inheriting from a virtual base with a non-trivial C++11 move assignment operator. This is dangerous because if the virtual base is reachable along more than one path, it is moved multiple times, which can mean both objects end up in the moved-from state. If the move assignment operator is written to avoid moving from a moved-from object, this warning can be disabled.
Warn if variable length array is used in the code. -Wno-vla prevents the -Wpedantic warning of the variable length array.
Warn if a register variable is declared volatile. The volatile modifier does not inhibit all optimizations that may eliminate reads and/or writes to register variables. This warning is enabled by -Wall.
Warn if a requested optimization pass is disabled. This warning does not generally indicate that there is anything wrong with your code; it merely indicates that GCC’s optimizers are unable to handle the code effectively. Often, the problem is that your code is too big or too complex; GCC refuses to optimize programs when the optimization itself is likely to take inordinate amounts of time.
-Wpointer-sign (C and Objective-C only)
Warn for pointer argument passing or assignment with different signedness. This option is only supported for C and Objective-C. It is implied by -Wall and by -Wpedantic, which can be disabled with -Wno-pointer-sign.
This option is only active when -fstack-protector is active. It warns about functions that are not protected against stack smashing.
Warn about string constants that are longer than the “minimum maximum” length specified in the C standard. Modern compilers generally allow string constants that are much longer than the standard’s minimum limit, but very portable programs should avoid using longer strings.The limit applies after string constant concatenation, and does not count the trailing NUL. In C90, the limit was 509 characters; in C99, it was raised to 4095. C++98 does not specify a normative minimum maximum, so we do not diagnose overlength strings in C++.

This option is implied by -Wpedantic, and can be disabled with -Wno-overlength-strings.

-Wunsuffixed-float-constants (C and Objective-C only)
Issue a warning for any floating constant that does not have a suffix. When used together with -Wsystem-headers it warns about such constants in system header files. This can be useful when preparing code to use with the FLOAT_CONST_DECIMAL64 pragma from the decimal floating-point extension to C99.
-Wno-designated-init (C and Objective-C only)
Suppress warnings when a positional initializer is used to initialize a structure that has been marked with the designated_init attribute.

iDev: Guidelines for installing custom enterprise apps on iOS

Guidelines for installing custom enterprise apps on iOS

Follow these security guidelines to install custom apps created for your organization.

Organizations can use the Apple Developer Enterprise Program to create proprietary enterprise apps for iOS devices and to distribute them to employees for internal use. Before one of these apps can be opened, it must be trusted.
Trust is established automatically if the app is installed by Mobile Device Management (MDM). If you install an app manually you must also manually establish trust as described below.

Apple recommends using an (MDM) solution to distribute the apps because it is secure and requires no user interaction. Users can also install these custom apps from a secure website operated by their organization. If you’re not installing an app from your organization, the best way to protect your iPhone, iPad, or iPod touch is to download and install apps only from the Apple App Store.

Manually Installing and Trusting an Enterprise App

When you first open an enterprise app you’ve manually installed, you see a notification that the developer of the app isn’t trusted on your device. You can dismiss this message but you can’t open the app.

After dismissing this message you can establish trust for this app developer. Tap Settings > General > Profiles or Profiles & Device Management. You then see a a profile for the developer under the “Enterprise App” heading.


Tap the profile to establish trust for this developer.


You’re then prompted to confirm your choice. Once you trust this profile, you can manually install other apps from the same developer and open them immediately. This developer remains trusted until you use the Delete App button to remove all apps from the developer.


An Internet connection is required to verify the app developer’s certificate when establishing trust. If you’re behind a firewall, make sure it’s configured to allow connections to If you aren’t connected to the Internet when you trust an app, the device displays “Not Verified” instead. In order to use the app, you need to connect to the Internet, and tap the Verify App button.

Original Source:

iDev: Learn Swift Tutorial Series

Hi Friends,

Hope you all doing good!!!

Now I am start posting to Learning the Swift Language (Apple introduce WWDC 2014). In every tutorial I put example to learn better and best practice way to do the coding.

My first post on Swift will be coming soon on August, In which I explain the basic of Swift and some sample code to understand the structure of Swift language.

Here a snaps of swift :


var colors = [“red”, “blue”]
var moreColors: String[] = [“orange”, “purple”] // explicit type
colors.append(“green”) // [red, blue, green]
colors += “yellow” // [red, blue, green, yellow]
colors += moreColors // [red, blue, green, yellow, orange, purple]

var days = [“mon”, “thu”]
var firstDay = days[0] // mon
days.insert(“tue”, atIndex: 1) // [mon, tue, thu]
days[2] = “wed” // [mon, tue, wed]
days.removeAtIndex(0) // [tue, wed]


class Counter {
var count: Int = 0
func inc() {
func add(n: Int) {
count += n
func printCount() {
println(“Count: \(count)”)

var myCount = Counter()
myCount.printCount() // Count: 3


let happy = true
if happy {
println(“We’re Happy!”)
} else {
println(“We’re Sad :(‘”)
// We’re Happy!

let speed = 28
if speed <= 0 {
} else if speed <= 30 {
println(“Safe speed”)
} else {
println(“Too fast!”)
// Safe speed

let n = 2
switch n {
case 1:
println(“It’s 1!”)
case 2…4:
println(“It’s between 2 and 4!”)
case 5, 6:
println(“It’s 5 or 6”)
println(“Its another number!”)
// It’s between 2 and 4!


let myInt = 1
myInt = 2 // compile-time error!


var days = [“mon”: “monday”, “tue”: “tuseday”]
days[“tue”] = “tuesday” // change the value for key “tue”
days[“wed”] = “wednesday” // add a new key/value pair

var moreDays: Dictionary = [“thu”: “thursday”, “fri”: “friday”]
moreDays[“thu”] = nil // remove thu from the dictionary
moreDays.removeValueForKey(“fri”) // remove fri from the dictionary


enum CollisionType: Int {
case Player = 1
case Enemy = 2
var type = CollisionType.Player

For Loops

for var index = 1; index < 3; ++index {
// loops with index taking values 1,2
for index in 1..3 {
// loops with index taking values 1,2
for index in 1…3 {
// loops with index taking values 1,2,3

let colors = [“red”, “blue”, “yellow”]
for color in colors {
println(“Color: \(color)”)
// Color: red
// Color: blue
// Color: yellow

let days = [“mon”: “monday”, “tue”: “tuesday”]
for (shortDay, longDay) in days {
println(“\(shortDay) is short for \(longDay)”)
// mon is short for monday
// tue is short for tuesday


func iAdd(a: Int, b: Int) -> Int {
return a + b
iAdd(2, 3) // returns 5

func eitherSide(n: Int) -> (nMinusOne: Int, nPlusOne: Int) {
return (n-1, n+1)
eitherSide(5) // returns the tuple (4,6)

Logical Operators

var happy = true
var sad = !happy // logical NOT, sad = false
var everyoneHappy = happy && sad // logical AND, everyoneHappy = false
var someoneHappy = happy || sad // logical OR, someoneHappy = true


let name = “swift”
println(“My name is \(name)”)
print(“See you “)
My name is swift
See you later


var myString = “a”
let myImmutableString = “c”
myString += “b” // ab
myString = myString + myImmutableString // abc
myImmutableString += “d” // compile-time error!

let count = 7
let message = “There are \(count) days in a week”


var myInt = 1
var myExplicitInt: Int = 1 // explicit type
var x = 1, y = 2, z = 3 // declare multiple integers
myExplicitInt = 2 // set to another integer value

Source Ref: Press Here

Thanks Friends:)

Keep Coding:)

Mishra Vinay
Solution’s Point

The 18 Most Important Features in iOS 8

At WWDC, developers rule. Apple may have previewed iOS 8 and OS X Yosemite to the entire world at its opening keynote, but developers are the only ones who get to check out the beta version of the software until an open beta program kicks off this summer.

This year’s conference has had its share of surprises, and it’s little wonder devs are salivating: Apple is allowing more flexibility about what developers can grow within its walled garden. For the first time, third-party onscreen keyboards will be welcomed in iOS 8, widgets are coming to the notification center, and media apps will have greater access to the device’s camera. Apple even debuted its own programming language, Swift, which got some of the loudest cheers during Monday’s keynote.

That’s all well and good, but what about the rest of us?

What’s in iOS 8 that will change the mobile life of your everyday iPhone user?

What’s in iOS 8 that will change the mobile life of your everyday iPhone user? Quite a bit, as it turns out. Here are the most important changes coming in iOS 8, based on whatApple revealed at WWDC and reports about the beta software:


1. Battery usage indicator

It’s probably the most common complaint about the iPhone: The battery drains too damn fast. This is, of course, dependent on exactly what you do with it, but how do users know whether to prioritize dimming the screen, quitting a particular app or turning off Background App Refresh?

In iOS 8, they’ll finally get some guidance. The iPhone’s settings will offer a way to checkexactly which apps and functions are draining your battery. With that guidance, users will be able to selectively change their settings or uninstall the right apps to maximize their battery.

Developers will certainly find the feature useful as well, as it should help make their apps more efficient. In short, this could be the most welcome new feature in iOS 8.

2. New keyboard(s)

iOS 8 keyboard

There’s nothing more fundamental to the iPhone than its onscreen keyboard — and in iOS 8, it gets an upgrade via predictive typing, which suggests several options for the next word as you type. This is a feature that’s been on Android for a while, although Apple says its implementation is superior — since it learns what you’re likely to say to different friends and colleagues.

At the same time, Apple is letting developers offer their own keyboards. You may have tried Swype for Android, for example, which uses an algorithm that lets you swipe around a keyboard rather than tap; the company has already said it will make its keyboard available for iOS.

3. Continuity



Apple took the idea of collaboration through the cloud to a new level with a new feature called Handoff, part of its “Continuity” concept. If you have an iPhone and a Mac, you’ll be able to start a task on one device (say, composing an email) and finish on the other. Since the devices are aware of each other, all you have to do is click one button, and it works on iPad, too.

Continuity also has a couple of bonuses: First, AirDrop will work between Macs and iOS devices. Second, using your iPhone as a personal hotspot has never been easier. There’s no configuration needed — the iPhone will just know when your Mac needs the connection.

4. New camera features

The camera is probably every smartphone’s No. 1 app. Apple likes to keep its interface relatively simple, but in iOS 8, users will get a couple of more options: a three-second timerand time-lapse capture for video — sort of the opposite of the slow-motion mode introduced in iOS 7. The camera also gets focus and exposure controls.

5. iCloud Photo Library

iCloud Photo Library

iCloud currently stores the last 1,000 photos from your iOS devices for free. With iOS 8, users will be able to upgrade to iCloud Photo Library, which will instantly upload all iPhone/iPad photos and videos to iCloud. Users only get 5GB for free, though — storage costs $0.99 a month for 20GB, with tiers all the way up to 1TB. (The Google+ app on iOS, by the way, will back up all your photos up to Google’s 15 GB limit, for free).

6. Family Sharing

Family Sharing


With iOS 8, Apple is taking the first step toward merging Apple IDs (a long-requested feature) by introducing Family Sharing, which lets different Apple users share all content they’ve downloaded from iTunes. Up to six people can be designated family members, and it provides a great solution to the problem of kids downloading paid apps on their parents’ credit cards: With Family Sharing, the parent gets notified, and then can grant or deny the purchase.

7. Interactive Notifications

Interactive Notifications


Just need to reply to a message with a single word? Why do you have to launch Messages for that? In iOS 8, you won’t have to — just pull down on the banner that appears and you can type your reply — then get right back to playing Candy Crush.

Notifications on the lock screen are interactive, too. Swiping an alert to the left will reveal Reply/Dismiss buttons, letting you do things faster without unlocking your phone. And if you’re concerned about security implications, you can disable this feature.

8. Messages upgrade

iOS 8 Messages 

In iOS 8, Apple’s built-in messaging app has a lot more to offer. Apple added the ability to send audio and video messages to your friends. With audio, they’re effortless: just open the conversation and raise the phone to your ear to begin recording. Users can also let these kinds of messages self-destruct after a certain amount of time — but that’s just a memory-management feature, and not, as has been claimed, an attempt to move in on Snapchat’s territory. (After all, there’s nothing to prevent the other people in the conversation from saving their versions of the video or audio.)

At the same time, Messages adds a couple of convenient features: You can set Do Not Disturb on specific threads so you’re not constantly getting alerts from big group messages. You can also now share your location with contacts you’re conversing with, as in the Find My Friends app, viewable through a new “Details” button on threads.

9. Widgets

iOS 8 widgets


Here’s another upgrade that Android has had a lock on for years: widgets, made possible byiOS 8’s “extensibility,” which allows apps to share data and functions with other apps.

Don’t get too excited — widgets will reside in the notification center, not the home screen. But their arrival on iOS is a big upgrade, and if Android is any indication, you can expect the floodgates to open for these small, “glanceable” mini-apps when iOS 8 launches in the fall.

10. Lock screen app suggestions

In iOS 8, users will notice a new icon on the iPhone lock screen that looks like the App Store. Swipe up and you’ll see app suggestions based on your location. For example, if you’re across the street from Starbucks, you might see the Starbucks app.

The feature could be a new path to app discoverability (which can be a problem for apps not in the Top 100), but we’ll wait to see how this plays out between Apple, vendors and developers.

11. TouchID for apps



Apple took fingerprint reading mainstream with the TouchID sensor in the iPhone 5S. In iOS 8, it’s going to open up that level of convenience to developers, who can let a user unlock any password stored in their keychain by placing their finger on the reader. That could potentially be even more convenient than Lastpass app logins on Android.

12. iCloud Drive

iCloud Drive 

If you’ve ever tried to save, say, a PDF from an email on your iPhone, you may have been frustrated by the lack of a native file system for iOS. Soon iCloud Drive will address that problem, while at the same time offering a cloud-storage service similar to Dropbox, Box or Google Drive. It’s compatible with Windows, too — but not Android.

13. Health



The new Health app is straightforward: It provides a central place for all the health and fitness information you’re storing on the iPhone. Many apps, such as Nike+ and Fitbit, do this individually, but now those apps will be able to integrate into one app — presuming developers take advantage of Apple’s HealthKit platform.

Apple is also partnering with healthcare providers to help bring the iPhone health data to the doctors and care specialists who can really do something with it. Health could have a profound effect on preventative medicine, if both developers and care centers support it.

14. New Siri features



Be careful what you say — Siri is always listening in iOS 8. Even if the iPhone is in a dormant state, you can just say “Hey Siri” to wake up the phone and ask something. The phone has to be plugged into power for this to work, indicating Apple probably sees it as a hands-free solution for the car.

Siri can also identify songs with built-in Shazam integration. So instead of launching an app, all you’ll need to do is hold down your iPhone’s home button to find out what music is playing. Think of all the time you’ll save at the bar.

15. Contacts on apps screen

iOS 8 Contacts


Apple realized it wasn’t making use of all the space on the apps screen that appears when you double-click the home button. Right above the apps running, you’ll see a strip of the most recent contacts along the top. It’s another welcome convenience.

16. More Spotlight results

iOS 8 Spotlight results


Searching on the iPhone in iOS 8 now brings up Wikipedia, App Store and iTunes results for anything you’re searching for.

17. Full-featured Safari

Safari got a huge upgrade in iOS 7, and although the upgrades in iOS 8 are more incremental (and already exist in other browsers), they’re welcome. There’s more flexibility in Private browsing, letting you keep regular and private tabs separate. DuckDuckGo — the privacy-preserving alternative to Google — is supported as a search engine, and users will be able to easily request the desktop version of any site.

18. The Weather Channel

In iOS 7, Apple’s weather app got its info from Yahoo. Starting in iOS 8, that data comes from the Weather Channel.

Have something to add to this story? Share it in the comments.

Source : Press HERE

Thanks 🙂

Solution’s Point

iDev: Change iOS project “My Mac 64-bit” to “iOS Device”

Hi Friends,

XCode iOS project only shows “My Mac 64-bit”!!!

The Simulator and Device options to Build/Run your have have disappeared.
This happened to  me after I changed the project name once or changed by another person.

solution #1:

  1. – Close Xcode.
  2. – Locate your Project folder.
  3. – Right-click on the AppName.xcodeproj file and click show package contents.
  4. – Now delete everything inside the xcuserdata folder.

If this does not work trying this:

  1. – open Xcode (obviously)
  2. – clicked on Manage Schemes and then Autocreate Schemes Now.
  3. – Then select the new scheme in Xcode.

Now you should get back all device/simulator options.

Thanks 🙂

Keep Coding 🙂

iDev: How to extend existing method in Objective-C

Hi Friends,

Todays you learn a very good technique, I hope:)

With blocks it’s more easy if you need extend your method. But if you will need extend some method of another class, not yours, and you will not be able to get the sources then this solution for you. (And if you will not be able or does not have any reason for creating a subclass)

1. You need create a category of class

2. import runtime in implementation file (.m)

#import <objc/runtime.h>

3. implement your method inside category, for example :

– (void) extend_method {

// your code

//  here will be performed the original method
[self extend_method];

// your code

It looks like this method has recursive calls itself, but it’s not true. Look next step

4. add method for replace (you can use +initialize or +load)

+ (void) initialize {
Method original = class_getInstanceMethod(self, @selector(method));
Method replacement = class_getInstanceMethod(self, @selector(extend_method));
method_exchangeImplementations(original, replacement);


Reference : Press Here

Keep Coding 🙂


iDev: iOS Device not detect by xcode-5

Hi Friends,

Today I found a one major issue with XCode, Actually I upgarde my iOS Devices (6.0 to 7.1 ) , after that my device not detected by Xcode 5.0,with this error on organizer,

“The version of iOS on “iPhone/iPad ” is not supported by this installation of the iOS SDK. Please restore the device to a version of the OS listed below, or update to the latest version of the iOS SDK; which is available here.”


Please upgrade your XCode to 5.1 and above version using the OS X App Store application, your reference links are :

And fix this issue.

For Reference : Here

Thanks 🙂


iDev: Design pattern are used on iOS Development other than MVC

Hi Friends,

Here the some list of design pattern with sort description


What is Design Pattern?

A design pattern is a common solution to a software problem. They are helpful for speeding up problem solving, ensuring
that a developer doesn’t have to re-invent the wheel for every situation. They also give developers a common vocabulary with which to get across high-level ideas with minimal explanation and full understanding.

Design patterns are everywhere in iOS Developement,Because iOS is a fairly specific platform, developers often face similar problems over and over, so there are a few design patterns that are extremely common in iOS.

Here is a short list of design patterns used by software engineers:

  • Abstract Factory Pattern
  • Adaptor Pattern
  • Object Modeling Pattern
  • Chain of Responsibility Pattern
  • Command Pattern
  • Composite Pattern
  • Decorator Pattern
  • Façade Pattern
  • Iterator Pattern
  • Mediator Pattern
  • Memento Pattern
  • Model-View-Controller Pattern
  • Observer Pattern
  • Proxy Pattern
  • Receptionist Pattern
  • Singleton Pattern
  • Template Method Pattern
  • S.O.L.I.D. Programming

On iOS :

Abstract Factory

The Abstract Factory pattern provides an interface for creating families of related or dependent objects without specifying their concrete classes. The client is decoupled from any of the specifics of the concrete object obtained from the factory.


The Adapter design pattern converts the interface of a class into another interface that clients expect. Adapter lets classes work together that couldn’t otherwise because of incompatible interfaces. It decouples the client from the class of the targeted object.

Chain of Responsibility

The Chain of Responsibility design pattern decouples the sender of a request from its receiver by giving more than one object a chance to handle the request. The pattern chains the receiving objects together and passes the request along the chain until an object handles it. Each object in the chain either handles the request or passes it to the next object in the chain.


The Command design pattern encapsulates a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undoable operations. The request object binds together one or more actions on a specific receiver. The Command pattern separates an object making a request from the objects that receive and execute that request.


The Composite design pattern composes related objects into tree structures to represent part-whole hierarchies. The pattern lets clients treat individual objects and compositions of objects uniformly. The Composite pattern is part of the Model-View-Controller aggregate pattern.


The Decorator design pattern attaches additional responsibilities to an object dynamically. Decorators provide a flexible alternative to subclassing for extending functionality. As does subclassing, adaptation of the Decorator pattern allows you to incorporate new behavior without modifying existing code. Decorators wrap an object of the class whose behavior they extend. They implement the same interface as the object they wrap and add their own behavior either before or after delegating a task to the wrapped object. The Decorator pattern expresses the design principle that classes should be open to extension but closed to modification.


The Facade design pattern provides a unified interface to a set of interfaces in a subsystem. The pattern defines a higher-level interface that makes the subsystem easier to use by reducing complexity and hiding the communication and dependencies between subsystems.


The Iterator design pattern provides a way to access the elements of an aggregate object (that is, a collection) sequentially without exposing its underlying representation. The Iterator pattern transfers the responsibility for accessing and traversing the elements of a collection from the collection itself to an iterator object. The Iterator defines an interface for accessing collection elements and keeps track of the current element. Different iterators can carry out different traversal policies.


The Mediator design pattern defines an object that encapsulates how a set of objects interact. Mediator promotes loose coupling by keeping objects from referring to each other explicitly, and it lets you vary their interaction independently. These objects can thus remain more reusable. A “mediator object” in this pattern centralizes complex communication and control logic between objects in a system. These objects tell the mediator object when their state changes and, in turn, respond to requests from the mediator object.


The Memento pattern captures and externalizes an object’s internal state—without violating encapsulation—so that the object can be restored to this state later. The Memento pattern keeps the important state of a key object external from that object to maintain cohesion.


The Observer design pattern defines a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically. The Observer pattern is essentially a publish-and-subscribe model in which the subject and its observers are loosely coupled. Communication can take place between the observing and observed objects without either needing to know much about the other.


The Proxy design pattern provides a surrogate, or placeholder, for another object in order to control access to that other object. You use this pattern to create a representative, or proxy, object that controls access to another object, which may be remote, expensive to create, or in need of securing. This pattern is structurally similar to the Decorator pattern but it serves a different purpose; Decorator adds behavior to an object whereas Proxy controls access to an object.


The Receptionist design pattern addresses the general problem of redirecting an event occurring in one execution context of an application to another execution context for handling. It is a hybrid pattern. Although it doesn’t appear in the “Gang of Four” book, it combines elements of the Command, Memo, and Proxy design patterns described in that book. It is also a variant of the Trampoline pattern (which also doesn’t appear in the book); in this pattern, an event initially is received by a trampoline object, so-called because it immediately bounces, or redirects, the event to a target object for handling.


The Singleton design pattern ensures a class only has one instance, and provides a global point of access to it. The class keeps track of its sole instance and ensures that no other instance can be created. Singleton classes are appropriate for situations where it makes sense for a single object to provide access to a global resource.

Template Method

The Template Method design pattern defines the skeleton of an algorithm in an operation, deferring some steps to subclasses. The Template Method pattern lets subclasses redefine certain steps of an algorithm without changing the algorithm’s structure.

Source: Cocoa Design Patterns.

Reference : Stackoverflow.


Thanks 🙂 Keep Coding…

iDev: iOS developers now can register up to 200 iOS devices for testing

As we all know the number of the products increasing for iOS, there is some good news for iOS developers. Apple has quietly increased the number of devices that can be registered to their developer account from 100 to 200.Apple_gray_logo

Since the launch of the App Store, Apple has allowed only 100 devices/UDIDs to be registered per developer license per year.


Although developers can remove devices from their account, they still get counted against their 100 device per year limit.

The 100 device limitation has been one of the biggest pain points for developers, especially since Apple has expanded its iOS product lineup to include the iPad and iPad mini. It is also extremely restrictive for companies that created number of apps per year.


Apple hasn’t updated its support documentation, so it is not official yet. but the before the rumored iphone lunch event updating this news defiantly helps the developers.

If you’re a developer we would love to know what you think of Apple’s decision to increase the UDID limit. Should Apple remove this restriction? or at least keep this cap at an app level?

Reference Link : Here

Thanks , Keep Coding 🙂