Jeremie Pelletier wrote:
Jérôme M. Berger wrote:Michel Fortin wrote:I fully support having a way to specify a default implementation for a function in an interface. It might get handy for a few things (like implementing the delegate pattern you see everywhere in Cocoa). But it's a bad replacement for contracts.Then what's the difference between an interface and an abstract class? I thought that the whole point of interfaces was that you couldn't have implementations of the methods so that you had no problem choosing an implementation when inheriting from multiple interfaces.JeromeThe interface supports multiple inheritance since it doesn't add to the vtable of the class using it,
?? The interface adds as much (or as little) to the vtable as another class would. The reason why interfaces support multiple inheritance is that since the interface does not contain the code for any of its methods, there is never any doubt which method should be called even if several ancestors have methods with the same signature. Once you add code to the interface you loose that advantage.
and its code would be implemented on the classes implementing the interface, not overridden by subclasses.
I don't see how that's different from standard class inheritance. After all there is nothing that forces you to override methods in subclasses if they already have an implementation in the parent class either.
Jerome
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