Inherit from a Singleton and a base class

Question

In my Unity game, I have one player and one enemy (it's a card game so this is always true). I use a basic Singleton base class to access them from any sub-system in the game, like this:

public abstract class Singleton<T> : MonoBehaviour where T : Component
{
    public static T instance;

    protected virtual void Awake()
    {
        if (instance != null) {
            string typename = typeof(T).Name;
            Debug.LogWarning($"More that one instance of {typename} found.");
        }
        instance = this as T;
    }
}

public class Player : Singleton<Player>
{
    public void DoSomething();
}

public class Enemy : Singleton<Enemy>
{
    public void DoSomething();
}

public class OtherPartOfGame : MonoBehaviour
{
    void Start() {
        Player.instance.DoSomething();
        Enemy.instance.DoSomething();
    }
}

But I want to pull out some common functionality into a base class CharacterBase. Of course normally I'd just do this:

public abstract class CharacterBase : MonoBehaviour
{
    public abstract void DoSomething();
}

public class Player : CharacterBase
{
    public override void DoSomething() {}
}

public class Enemy : CharacterBase
{
    public override void DoSomething() {}
}

But how do I also keep my generic Singleton in the mix, without using multiple inheritance?

Answer 1

Well the easiest way would be to just let your CharacterBase class inherit from Singleton like this

public abstract class CharacterBase<T> : Singleton<T> where T : Component
{
    public abstract void DoSomething();
}

and then do

public class Player : CharacterBase<Player>
{
    public override void DoSomething() { ... }
}

public class Enemy : CharacterBase<Enemy>
{
    public override void DoSomething() { ... }
}

Everything else would just complicate it for no good reason.