Issue with Inheritance when using nested Generic classes in C#

Question

I\'m trying to create a class hierarchy such that I can have:

SpecificScreenController < ScreenController < Singleton

So far I have these set up as:

Answer 1

The problem here is one of covariance. You're assuming that if SpecificScreenController inherits from MonoBehaviour then ScreenController<SpecificScreenController> also inherits from ScreenController<MonoBehaviour>. It doesn't. You can't do this cast.

Answer 2

As there seem to be no really clean solutions to this issue I ended up removing Singleton from my class hierarchy and copy-pasted non-generic versions of the singleton property get/instantiate code into each of the classes that I wanted to be singletons.

public abstract class ScreenController : MonoBehaviour
{
}

public class SpecificScreenController : ScreenController
{
    private static SpecificScreenController _instance;
    public static SpecificScreenController Instance{ get{... return _instance;} 
}