3 ms·

What exactly is the bad idea here? Having more than one method in a duck-type?

• steveklabnik 16y ago
  is_a? and respond_to? are code smells.
  • limmeau 16y ago
    Yes, I agree. I wasn't actually suggesting to sprinkle instanceof-checks throughout the code. What I was trying to get to: if you accept the existence of single-method ducktypes (like "things that have a walk() method" oder "things that have a quack() method"), then by intersecting these concepts, you arrive at things just like interfaces, whether you call them interfaces or not. If you want the pond system to work with your two-legged bird-sound robot, you perform the same mental steps as when implementing an interface. Hence, ducktypes could be seen as interfaces without an instanceof-operation.