-forwardInvocation for class methods
===

I'm struggling to forward a class method through a facade class.

To clarify, I'm overriding all the following methods:

    -(NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector
    -(void)forwardInvocation:(NSInvocation *)anInvocation
    +(BOOL)instancesRespondToSelector:(SEL)aSelector
    +(NSMethodSignature *)instanceMethodSignatureForSelector:(SEL)aSelector
    +(IMP)instanceMethodForSelector:(SEL)aSelector
    +(BOOL)resolveClassMethod:(SEL)sel
    +(BOOL)resolveInstanceMethod:(SEL)sel

.. and yet, for the class method, the only one to be called is `+resolveClassMethod`. From there, I immediately get an unrecognized selector exception regardless of whether I return YES or NO.   

What's going on?  
Does class message forwarding work differently to instance message forwarding?  
Similarly, why isn't there a `+forwardInvocation` class method?

Any help would be greatly appreciated.