nscollection view using cocoa

i i tried to integrate the icon Collection sample of apple docs in my application but it throws error:

@interface MyViewController : NSViewController <NSCollectionViewDelegate> 

shows error in my project as "Cannot find protocol declar开发者_C百科ation for NSCollectionViewDelegate"

please help somebody.

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You need to #import the file where that protocol is defined into the header where you declare your class.