Automatically Taking a Screenshot?

I'm developing using the cocos2d framework, Obj-C. I have a whole method for taking a screenshot called "screenshot". I'd l开发者_运维技巧ike to know how I can take a screenshot. I've been told to just call [self screenshot]; but I get the warning 'GameOver' (class) may not respond to '-screenshot'. The screenshot method is in the AppDelegate.

Any help is appreciated!

Include the header for the application delegate and call.

[[[UIApplication sharedApplication] delegate] screenshot]