IPhone Development -- Unresolved Symbols CAKeyframeAnimation: iOS Anima

I tried to use CoreAnimation for some animation effects, but the following compilation error was prompted at the end:

[Plain]
Undefined symbols for architecture i386:
"_ OBJC_CLASS _ $ _ CAKeyframeAnimation", referenced from:
Objc-class-ref in SpellPageViewController. o
Ld: symbol (s) not found for architecture i386
Collect2: ld returned 1 exit status

Undefined symbols for architecture i386:
"_ OBJC_CLASS _ $ _ CAKeyframeAnimation", referenced from:
Objc-class-ref in SpellPageViewController. o
Ld: symbol (s) not found for architecture i386
Collect2: ld returned 1 exit status
Solution:

Check whether you have linked the QuartzCore library. If there is no link, put it in the frameWork.