SingletonMonoBehaviour.cs

using UnityEngine;
 
public class SingletonMonoBehaviour<T> : MonoBehaviour where T : MonoBehaviour
{
    private static T instance;
    public static T Instance {
        get {
            if (instance == null) {
                instance = (T)FindObjectOfType(typeof(T));
 
                if (instance == null) {
                    Debug.LogError (typeof(T) + "is nothing");
                }
            }
 
            return instance;
        }
    }
 
 
}