What does the -ObjC linker flag do?

I have an app that works with and without the linker flag. However, without the linker flag, I get a very different 开发者_StackOverflow中文版behaviour when adding data to a view.

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This flag causes the linker to load every object file in the library that defines an Objective-C class or category. While this option will typically result in a larger executable (due to additional object code loaded into the application), it will allow the successful creation of effective Objective-C static libraries that contain categories on existing classes.

From this Technical Q&A