Suppressing that particular warning is not safe. The compiler needs to know the types of the arguments and returns to a method to generate correct code.
With Objective-C, a number of serious errors only appear as warnings. Not only do I 永远不会 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.
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: