iphone CATiledLayer not recognized as class?

Im following the apple ZoomingPDFViewer example, I have the frameworks just as in the example, but when I write in xcode the class CATiledLayer doesnt get recognized in the edit area (no coming purple as a class, like in the example, and comand click on that word an开发者_StackOverflowd doesnt recognize it), what am I missing ??

     CATiledLayer *tiledLayer = (CATiledLayer *)[self layer];

I build the project and get no error or warning, but why it doesnt recognize the class?

EDIT>

changed project get info settings as suggested, but still not working!

• changed the compiler from GCC 4.2 to LLVM GCC 4.2.
• changed the Project Format to match the version of Xcode I'm using ("Xcode 3.2-compatible").
• click "Rebuild Code Sense Index" button.

still not working!, what could it be?, it appears working in apple sample code, but not in mine?? What would I be missing?

thanks in advance!!

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Check out xcode code sense color/completion not working