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I have following structure of objects: Animal, Dog and Cat. As You expect Dog and Cat are inherited from Animal. And I've a farm class: @implementation AnimalFarm -(Animal*) createAnimal:(AnimalType)type{ switch (type) { case CAT: return [Cat new]; case DOG: return [Dog new]; default: return [Animal new]; } } @end and I tried to unit test: AnimalFarm *farm = [AnimalFarm new]; Animal *dog = [farm createAnimal:DOG]; Animal *cat = [farm createAnimal:CAT]; STAssertTrue([cat isMemberOfClass:[Cat class]],@"cat is not a cat!"); STAssertTrue([dog isMemberOfClass:[Dog class]],@"Dog is not a dog!"); STAssertTrue([cat isKindOfClass:[Animal class]],@"Cat is not an animal!"); STAssertTrue([dog isKindOfClass:[Animal class]],@"Cat is not an animal!"); Implementation of classes: @interface Cat : Animal { } @end @implementation Cat -(NSString*) say{ return @"miau"; } @end Implementation of dog is similar. but neither isKindOfClass or isMemberOfClass worked as I expected.... Am I missing something? When I use IFs instead of switch then everything goes well ... but what is the difference? Implementation of createAnimal which works: -(Animal *) createAnimal:(AnimalType)type { if (type == DOG) { return [Dog new]; } else if (type == CAT) { return [Cat new]; } else { return [Animal new]; }

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