How to Implement Interface with Enum Specific to Derived Class in C#?

Question

I'm trying to write an interface such as...

interface MyInterface
{
    MyObject Set(REGISTER register, PIN pin);
}

Both REGISTER and PIN are enums. The problem I'm running into is that REGISTER is defined in my MyBaseClass and PIN is defined in MyDerivedClass. I can live with using something like MyBaseClass.REGISTER in the interface, but that won't work for PIN. Every derivation of MyBaseClass will have a different enumeration for PIN. I found this other answer on SO, which seems to partially solve the problem, but it's not clear how I should then implement the function in MyDerivedClass. Does anyone have a solution for this?

Why wouldnt your enums just be in their own files and not defined inside a class? Or am I misunderstanding — maccettura, Oct 17 '18 at 20:49

score 4 · Accepted Answer · answered Oct 17 '18 at 20:53

Try using generics:

interface MyInterface<TPin>
{
    MyObject Set(Register register, TPin pin);
}

When you implement it in each derived class, you have to tell it what the type of the pin enum is:

class MyImplementation : MyInterface<MyPin>
{
    MyObject Set(Register register, MyPin pin)
    {
        // ...
    }
}

This means that you can't have a list of MyInterface objects, but you can have a list of MyInterface<SomePin> objects. And that makes sense - if the enum is different for each implementation, then given a MyInterface, how would you know what values to pass it?

How to Implement Interface with Enum Specific to Derived Class in C#?

1 Answers1