Unity MonoBehaviour Singleton

Singleton.cs

using System;
using UnityEngine;

namespace FarFarEast
{
    /// <summary>
    /// Inherit from this base class to create a singleton.
    /// e.g. public class MyClassName : Singleton<MyClassName> {}
    /// </summary>
    public class Singleton<T> : MonoBehaviour where T : MonoBehaviour
    {
        // Check to see if we're about to be destroyed.
        private static bool m_ShuttingDown = false;
        private static Lazy<T> m_Instance = new Lazy<T>(Factory);

        private static T Factory()
        {
            // Search for existing instance.
            T instance = (T)FindObjectOfType(typeof(T));

            // Create new instance if one doesn't already exist.
            if (instance == null)
            {
                // Need to create a new GameObject to attach the singleton to.
                var singletonObject = new GameObject();
                instance = singletonObject.AddComponent<T>();
                singletonObject.name = typeof(T).ToString() + " (Singleton)";

                // Make instance persistent.
                DontDestroyOnLoad(singletonObject);
            }
            return instance;
        }

        /// <summary>
        /// Access singleton instance through this propriety.
        /// </summary>
        public static T Instance
        {
            get
            {
                if (m_ShuttingDown)
                {
                    Debug.LogWarning("[Singleton] Instance '" + typeof(T) + "' already destroyed. Returning null.");
                    return null;
                }
                return m_Instance.Value;
            }
        }

        private void OnApplicationQuit()
        {
            m_ShuttingDown = true;
        }

        private void OnDestroy()
        {
            m_ShuttingDown = true;
        }
    }
}

Why do you use a lock statement? Because multithreading is not supported here 🤔

Why do you use a lock statement? Because multithreading is not supported here 🤔

You are right. The lock is most likely necessary, or can be done better. I forked this file without change a while back. Let me give it a shot.