What is the difference between the isKindOfClass:(Class)aClass
and the isMemberOfClass:(Class)aClass
functions?
I know it is something small like,
Because of class clusters, isMemberOfClass can give you an answer you might not expect. In many cases your best choice is more likely to be -(BOOL)conformsToProtocol:(SEL)aSelector or - (BOOL)conformsToProtocol:(Protocol*)aProtocol. I.e, it's better to test these if they can answer your need rather than testing class/subclass.
See apple doc for NSObject class and protocol:
http://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSObject_Class/Reference/Reference.html#//apple_ref/occ/cl/NSObject
http://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Protocols/NSObject_Protocol/Reference/NSObject.html#//apple_ref/occ/intf/NSObject