Extend interface to an abstract class

Question

I have an interface (move) that should move some shapes.

interface Move { move(); }
abstract class Shape : Move

class Circle : Shape
class Square : Shape
class Triangle : Shape

My doubt is, I must have an interface which moves Shapes but only Circle and Triangle should be able to be moved, so how do I "remove" the interface from Square? Should I remove the interface from Shape and add it manually on Circle and Triangle? I'm kinda confused with this. Hope someone can help me out.

Answer 1

You should setup your classes like this:

interface IMovable { move(); } 
abstract class Shape : { } 

class Circle : Shape, IMovable { } 
class Square : Shape { } 
class Triangle : Shape, IMovable { } 

If not every shape can be moved then Shape must not implement the interface. Also note I renamed your interface to IMovable, it's not a huge deal but it's more accepted and a better naming convention.

Answer 2

You can't remove an interface from an inheritance tree.

What you model appears to need two abstract classes - Shape and MovableShape.

interface IMove { move(); } 
abstract class Shape : {} 
abstract class MovableShape : IMove, Shape {} 

class Circle : MovableShape{}
class Square : Shape{}
class Triangle : MovableShape{}