forward class and corresponding @interface may not exist warning

출처: http://stackoverflow.com/questions/322597/objective-c-class-vs-import

 you see this warning:

warning: receiver 'myCoolClass' is a forward class and corresponding @interface may not exist

you need to #import the file, but you can do that in your implementation file (.m), and use the @class declaration in your header file.

@class does not (usually) remove the need to #import files, it just moves the requirement down closer to where the information is useful.

결국 import 잘못하면 그렇게 된다는 얘기