Warning Messages in Xcode
Compiler Warnings for Objective-C Developers is a good post for describing warning messages for Objective-C in xcode. A Chinese version can be found 谈谈Objective-C的警告.
Some important things are marked here.
Two ways to modify complier’s warning setting: UI Method and Custom Compiler Flags Method.
UI Method
In Project Navigator, choose the project. On the right, under Build Settings, Apple LLVM 6.1 - Warnings - Objective c and Apple LLVM 6.1 - Warnings - Objective C and ARC are Objective C specific settings. You may also want to see some setttings for all languages, including Objective C in Apple LLVM 6.1 - Warnings - All languages.
Custom Compiler Flags Method
Under Build Settings, find other warning flags in Apple LLVM 6.1 - Custom Compiler Flags. In this section, you can use -W... like commands for warning settings.
For example, use -Wall to display all warnings (actually, not All), use -Wno-unused-variable to indicate not displaying unused variable warnings. Use space between differenct commands, like -Wall -Wno-unused-variable.
Using this way, we can set for all kinds of warnings, some of which can not be set by UI Method above.
Go to the following two refrences for details on -Wall, -Wextra and -Weverything:
The following paragraph comes from the first reference:
If you encounter a particular warning that you actively want to suppress, check the build log. The compiler will tell you the name of each warning it has issued (-Wunused-variable in this example). You can use this name to selectively disable (with -Wno-unused-variable) or enable this specific warning in your project. In my experience, you will come up with a very short list of warnings you want to disable (probably no more than a handful).
Attach one image to indicate the place (red circles) to find the warning type:
