Why am I seeing an error about _OBJC_CLASS_$_CPGraphHostingView with Core Plot?

I downloaded the 开发者_高级运维Core Plot example application, but when I compile it I saw a few errors. I then added the Core Plot SDK, but in this SDK there is no class named CPGraphHostingView. Therefore, I added the class manually from this link.

However, I now see the following error:

ERROR -  "_OBJC_CLASS_$_CPGraphHostingView", referenced from:

How can I work around this to get the sample application to compile?

Follow the step-by-step instructions on the Core Plot wiki and you should be fine.

Note that the SDK install is considered experimental at this time, and I know that others have reported issues with using it, so I'd recommend following the instructions for using the static library instead.