iphone sdk CATransition 錯誤

CATransition *myTransition=[CATransitionanimation];

   // myTransition.timingFunction=UIViewAnimationCurveEaseIn;

    myTransition.type=kCATransitionPush;

    if(page>lastViewed){

        myTransition.subtype=kCATransitionFromRight;

    }else{

        myTransition.subtype=kCATransitionFromLeft;

    }

Undefined symbols for architecture i386:

  "_OBJC_CLASS_$_CATransition", referenced from:

      objc-class-ref in RootViewController.o

  "_kCATransitionFromLeft", referenced from:

      -[RootViewController setPage] in RootViewController.o

  "_kCATransitionFromRight", referenced from:

      -[RootViewController setPage] in RootViewController.o

  "_kCATransitionPush", referenced from:

      -[RootViewController setPage] in RootViewController.o

ld: symbol(s) not found for architecture i386

clang: error: linker command failed with exit code 1 (use -v to see invocation)

原因是少加了包 “ QuartzCore.framework”