Question

I have an interface so class writers are forced to implement certain methods. I also want to allow some default implemented methods, so I create a abstract class. The problem is that all classes inherit from the base class so I have some helper functions in there.

I tried to write : IClass in with the abstract base, but I got an error that the base didn’t implement the interface. Well of course because I want this abstract and to have the users implement those methods. As a return object if I use base I can’t call the interface class methods. If I use the interface I can’t access base methods.

How do I make it so I can have these helper classes and force users to implement certain methods?

Answer 1

Move the interface methods into the abstract class and declare them abstract as well. By this, deriving classes are forced to implement them. If you want default behaviour, use abstract classes, if you want to only have the signature fixed, use an interface. Both concepts don’t mix.