Initial Commit

Assets/Imstk/Scripts/Utility/Singleton.cs

@@ -0,0 +1,49 @@
+/*=========================================================================
+
+   Library: iMSTK-Unity
+
+   Copyright (c) Kitware, Inc. 
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+      http://www.apache.org/licenses/LICENSE-2.0.txt
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+
+=========================================================================*/
+
+using UnityEngine;
+
+namespace ImstkUnity
+{
+    // Simple singleton class as per https://blog.yarsalabs.com/using-singletons-in-unity/
+    // More powerful version is https://gist.github.com/rickyah/271e3aa31ff8079365bc
+    public class Singleton<T> : MonoBehaviour where T : MonoBehaviour
+    {
+        private static T _instance;
+        public static T Instance()
+        {
+            if (_instance == null)
+            {
+                _instance = FindObjectOfType<T>();
+                if (_instance == null)
+                {
+                    _instance = new GameObject(typeof(T).Name).AddComponent<T>();
+                }
+            }
+            else if (_instance != FindObjectOfType<T>())
+            {
+                Destroy(FindObjectOfType<T>());
+            }
+            // Need to check if this is necessary
+            // DontDestroyOnLoad(_instance.gameObject);
+            return _instance;
+        }
+    }
+}