Is there a way to suppress warnings in Xcode?

To disable warnings on a per-file basis, using Xcode 3 and llvm-gcc-4.2 you can use:

#pragma GCC diagnostic ignored "-Wwarning-flag"

Where warning name is some gcc warning flag.

This overrides any warning flags on the command line. It doesn't work with all warnings though. Add -fdiagnostics-show-option to your CFLAGS and you can see which flag you can use to disable that warning.

there is a simpler way to suppress Unused variable warnings:

#pragma unused(varname)

EDIT: source: http://www.cocoadev.com/index.pl?XCodePragmas

UPDATE: I came accross with a new solution, a more robust one

1. Open the Project > Edit Active Target> Build tab.
2. Under User-Defined: find (or create if you don't find one )the key : GCC_WARN_UNUSED_VARIABLE set it to NO.

EDIT-2 Example:

BOOL ok = YES;
NSAssert1(ok, @"Failed to calculate the first day the month based on %@", self);

the compiler shows unused variable warning for ok.

Solution:

BOOL ok = YES;
#pragma unused(ok)
NSAssert1(ok, @"Failed to calculate the first day the month based on %@", self);

PS: You can also set/reset other warning: GCC_WARN_ABOUT_RETURN_TYPE : YES/NO

For gcc you can use

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wshadow-ivar"
// your code
#pragma GCC diagnostic pop

You can learn about GCC pragma here and to get the warning code of a warning go to the Report Navigator (Command+9), select the topmost build, expand the log (the '=' button on the right), and scroll to the bottom and there your warning code is within square brackets like this [-Wshadow-ivar]

For clang you can use

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wshadow-ivar"
// your code
#pragma clang diagnostic pop

In order to surpress a warning for an individual file do the following:

select the file in the xcode project. press get info go to the page with build options enter -Wno- to negate a warning:

-Wno-

e.g.

-Wno-unused-parameter

You can get the name of the warning if you look on the project settings look at the GCC warnings located at the bottom of the build tab page, by clicking on each warning it will tell you the warning parameter name:

e.g.

Warn whenever a function parameter is unused aside from its declaration. [GCC_WARN_UNUSED_PARAMETER, -Wunused-parameter]

With Objective-C, a number of serious errors only appear as warnings. Not only do I never disable warnings, I normally turn on "Treat warnings as errors" (-Werror).

Every type of warning in your code can be avoided by doing things correctly (normally by casting objects to the correct type) or by declaring prototypes when you need them.