+ (Class)layerClass won't work

I'm building an OpenGL application and on eaglview.m + (Class)layerClass wont work.

If 开发者_C百科i try to run it I get:

"Undefined symbols for architecture i386:
  "_OBJC_CLASS_$_CAEAGLLayer", referenced from:
      objc-class-ref in GLView.o
ld: symbol(s) not found for architecture i386
collect2: ld returned 1 exit status"

How can I fix this?

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You need to add the OpenGL and potentially the QuartzCore frameworks to the target to link them.