Question

I have 3 interfaces with 2 methods each doing the same job.

Interface A
{
   Void M1()
   Void M2()
}

Interface B
{
   Void M1()
   Void M2()
}

Interface C
{
   Void M1()
   Void M2()
}

Now, There are 3 classes implementing each of these interfaces.

Public Class A1:A
{
  Public void M1()
  {

  }
  Public void M2()
  {

  }
}

Public Class B1:B
{
  Public void M1()
  {

  }
  Public void M2()
  {

  }
}

Public Class C1:C
{
  Public void M1()
  {

  }
  Public void M2()
  {

  }
}

Functionality of M1 and M2 is exactly same in 3 classes. Interfaces are a part of library, I cannot change the interface and also cannot declare a new interface.

I want to refactor this code so that this duplication can be removed. I thought of creating a common class containing this functionality and then calling common class from each of these classes.

Please suggest.

Answer 1

It sounds like you should declare your own interface, and then create an adapter – or possibly multiple adapters. For example:

public interface IUnified
{
    void M1();
    void M2();
}

public class UnifiedAdapter : IUnified
{
    private Action m1;
    private Action m2;

    public UnifiedAdapter(A a)
    {
        m1 = () => a.M1();
        m2 = () => a.M2();
    }

    public UnifiedAdapter(B b)
    {
        m1 = () => b.M1();
        m2 = () => b.M2();
    }

    public UnifiedAdapter(C c)
    {
        m1 = () => c.M1();
        m2 = () => c.M2();
    }

    public M1()
    {
        m1();
    }

    public M2()
    {
        m2();
    }
}

(This uses delegates to avoid having to create multiple adapter classes. The best approach depends on your exact situation.)