Create ModSingleton.cs

IPA.Loader/Utilities/ModSingleton.cs

@@ -0,0 +1,91 @@
+using UnityEngine;
+
+namespace IPA.Utilities
+{
+    /// <summary>
+    /// Generate a persistent singleton which can be destroyed.
+    /// </summary>
+    /// <typeparam name="T"></typeparam>
+    public class ModSingleton<T> : MonoBehaviour where T : MonoBehaviour
+    {
+        /// <summary>
+        /// The stored reference for the instance
+        /// </summary>
+        protected static T _instance;
+        /// <summary>
+        /// The lock for the instance to prevent more than one being created.
+        /// </summary>
+        protected static object _lock = new object();
+
+        /// <summary>
+        /// Checks to see if the singleton if the singleton can be accessed
+        /// </summary>
+        public static bool IsSingletonAvailable => _instance != null;
+
+        /// <summary>
+        /// Noncapitalized version which points to the actual property.
+        /// </summary>
+        public static T instance => Instance;
+
+        /// <summary>
+        /// Creates and or returns the singleton
+        /// </summary>
+        public static T Instance
+        {
+            get
+            {
+                T result;
+                object @lock = _lock;
+                lock (@lock)
+                {
+                    if (_instance == null)
+                    {
+                        _instance = (T)((object)FindObjectOfType(typeof(T)));
+                        if (FindObjectsOfType(typeof(T)).Length > 1)
+                        {
+                            IPA.Logging.Logger.log.Warn($"[Singleton] Something went really wrong - there should never be more than one singleton of {nameof(T)}");
+                            return _instance;
+                        }
+                        if (_instance == null)
+                        {
+                            GameObject gameObject = new GameObject();
+                            _instance = gameObject.AddComponent<T>();
+                            gameObject.name = $"{nameof(T)} Singleton";
+                            DontDestroyOnLoad(gameObject);
+                        }
+                    }
+                    result = _instance;
+                }
+                return result;
+            }
+        }
+
+        /// <summary>
+        /// Called when the singleton is enabled to prevent the singleton from being destroyed naturally
+        /// </summary>
+        private void OnEnabled()
+        {
+            DontDestroyOnLoad(this);
+        }
+
+        /// <summary>
+        /// Destroys the singleton.
+        /// </summary>
+        public static void Destroy()
+        {
+            if (_instance != null)
+            {
+                _lock = new object();
+                Destroy(_instance);
+            }
+        }
+
+        /// <summary>
+        /// Touches the instance to easily create it without having to assign it.
+        /// </summary>
+        public static void TouchInstance()
+        {
+            _ = Instance == null;
+        }
+    }
+}