public class MyClass : MonoBehaviour { void Awake () { Debug.Log(Manager.Instance.myGlobalVar); } }

public class Manager : Singleton<Manager> { protected Manager () {} // guarantee this will be always a singleton only - can't use the constructor!   public string myGlobalVar = "whatever"; }

using UnityEngine;   /// <summary> /// Be aware this will not prevent a non singleton constructor /// such as `T myT = new T();` /// To prevent that, add `protected T () {}` to your singleton class. /// /// As a note, this is made as MonoBehaviour because we need Coroutines. /// </summary> public class Singleton<T> : MonoBehaviour where T : MonoBehaviour { private static T _instance;   private static object _lock = new object();   public static T Instance { get { if (applicationIsQuitting) { Debug.LogWarning("[Singleton] Instance '"+ typeof(T) + "' already destroyed on application quit." + " Won't create again - returning null."); return null; }   lock(_lock) { if (_instance == null) { _instance = (T) FindObjectOfType(typeof(T));   if ( FindObjectsOfType(typeof(T)).Length > 1 ) { Debug.LogError("[Singleton] Something went really wrong " + " - there should never be more than 1 singleton!" + " Reopening the scene might fix it."); return _instance; }   if (_instance == null) { GameObject singleton = new GameObject(); _instance = singleton.AddComponent<T>(); singleton.name = "(singleton) "+ typeof(T).ToString();   DontDestroyOnLoad(singleton);   Debug.Log("[Singleton] An instance of " + typeof(T) + " is needed in the scene, so '" + singleton + "' was created with DontDestroyOnLoad."); } else { Debug.Log("[Singleton] Using instance already created: " + _instance.gameObject.name); } }   return _instance; } } }   private static bool applicationIsQuitting = false; /// <summary> /// When Unity quits, it destroys objects in a random order. /// In principle, a Singleton is only destroyed when application quits. /// If any script calls Instance after it have been destroyed, /// it will create a buggy ghost object that will stay on the Editor scene /// even after stopping playing the Application. Really bad! /// So, this was made to be sure we're not creating that buggy ghost object. /// </summary> public void OnDestroy () { applicationIsQuitting = true; } }

static public class MethodExtensionForMonoBehaviourTransform { /// <summary> /// Gets or add a component. Usage example: /// BoxCollider boxCollider = transform.GetOrAddComponent<BoxCollider>(); /// </summary> static public T GetOrAddComponent<T> (this Component child) where T: Component { T result = child.GetComponent<T>(); if (result == null) { result = child.gameObject.AddComponent<T>(); } return result; } }