MonoBehaviourSingleton

MonoBehaviourSingleton.cs

using UnityEngine;

namespace Game
{
    public class MonoBehaviourSingleton<T> : MonoBehaviour where T : Component
    {
        /// <summary>
        /// The instance of the singleton.
        /// </summary>
        protected static T _instance = null;

        /// <summary>
        /// This flag is used to check if the instance is destroyed or not.
        /// </summary>
        protected static bool _isDestroyed = false;

        /// <summary>
        /// Simple lock object to prevent multi-threading issues.
        /// </summary>
        protected static object _padlock = new object();

        /// <summary>
        /// Get the instance of the singleton.
        /// </summary>
        public static T Instance
        {
            get
            {
                if (_isDestroyed)
                {
                    return null;
                }

                if (_instance == null)
                {
                    lock (_padlock)
                    {
                        _instance = FindObjectOfType<T>();
                        if (_instance == null)
                        {
                            GameObject obj = new GameObject();
                            obj.name = typeof(T).Name + " Auto-Generated";
                            _instance = obj.AddComponent<T>();
                        }
                    }

                }
                return _instance;
            }
        }

        protected virtual void Awake()
        {
            InitSingleton();
        }

        protected virtual void OnDestroy()
        {
            _isDestroyed = true;
        }

        /// <summary>
        /// This method is logic that you need to initialize the singleton.
        /// </summary>
        protected virtual void InitSingleton()
        {
            if (_instance != null && _instance != this)
            {
                Destroy(this.gameObject);

                return;
            }

            _isDestroyed = false;
            _instance = this as T;
            DontDestroyOnLoad(this.gameObject);
        }
    }
}