How to subclass a SkankySDK class? e.g. QCRenderInImage

[subtleGradient]

I wanted to create a QCRenderInImage subclass that did some extra fancy jazz.
If you try this, it results in the following linker error…

Build Step

Ld /Users/aylott/Library/Developer/Xcode/DerivedData/QCRenderInImage-subclass-abuurssijdhzpzgponyawqfdzcte/Build/Products/Debug/QCRenderInImage-subclass.plugin/Contents/MacOS/QCRenderInImage-subclass normal x86_64
    cd /Users/aylott/Desktop/QCRenderInImage-subclass
    setenv MACOSX_DEPLOYMENT_TARGET 10.8
    /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang\
        -arch x86_64\
        -bundle\
        -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk\
        -L/Users/aylott/Library/Developer/Xcode/DerivedData/QCRenderInImage-subclass-abuurssijdhzpzgponyawqfdzcte/Build/Products/Debug\
        -F/Users/aylott/Library/Developer/Xcode/DerivedData/QCRenderInImage-subclass-abuurssijdhzpzgponyawqfdzcte/Build/Products/Debug\
        -F/Applications/Xcode.app/Contents/Developer/Library/Frameworks\
        -F/Library/Frameworks\
        -filelist /Users/aylott/Library/Developer/Xcode/DerivedData/QCRenderInImage-subclass-abuurssijdhzpzgponyawqfdzcte/Build/Intermediates/QCRenderInImage-subclass.build/Debug/QCRenderInImage-subclass.build/Objects-normal/x86_64/QCRenderInImage-subclass.LinkFileList\
        -mmacosx-version-min=10.8\
        -fobjc-link-runtime\
        -framework Cocoa\
        -framework Quartz\
        -o /Users/aylott/Library/Developer/Xcode/DerivedData/QCRenderInImage-subclass-abuurssijdhzpzgponyawqfdzcte/Build/Products/Debug/QCRenderInImage-subclass.plugin/Contents/MacOS/QCRenderInImage-subclass

Result

Undefined symbols for architecture x86_64:
  "_OBJC_CLASS_$_QCRenderInImage", referenced from:
      _OBJC_CLASS_$_QCRenderInImageFancy in QCRenderInImageFancy.o
     (maybe you meant: _OBJC_CLASS_$_QCRenderInImage_subclassPrincipal, _OBJC_CLASS_$_QCRenderInImageFancy )
  "_OBJC_METACLASS_$_QCRenderInImage", referenced from:
      _OBJC_METACLASS_$_QCRenderInImageFancy in QCRenderInImageFancy.o
     (maybe you meant: _OBJC_METACLASS_$_QCRenderInImage_subclassPrincipal, _OBJC_METACLASS_$_QCRenderInImageFancy )
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)