Interface vs Base class

Question

When should I use an interface and when should I use a base class?

Should it always be an interface if I don\'t want to actually define a base implementation of the

Answer 1

In general, you should favor interfaces over abstract classes. One reason to use an abstract class is if you have common implementation among concrete classes. Of course, you should still declare an interface (IPet) and have an abstract class (PetBase) implement that interface.Using small, distinct interfaces, you can use multiples to further improve flexibility. Interfaces allow the maximum amount of flexibility and portability of types across boundaries. When passing references across boundaries, always pass the interface and not the concrete type. This allows the receiving end to determine concrete implementation and provides maximum flexibility. This is absolutely true when programming in a TDD/BDD fashion.

The Gang of Four stated in their book "Because inheritance exposes a subclass to details of its parent's implementation, it's often said that 'inheritance breaks encapsulation". I believe this to be true.