fix: MonoSingleton and MonoBehaviourCallback improvements (#112)

* fix: solid MonoBehaviourCallback impl + MonoSingleton fix

* fix: made MonoSingleton.Instantiate method private, added test for single Instance validation

* chore: incremented version to 2.0.0 due to breaking changes

Runtime/Async/Coroutine/MonoBehaviourCallback.cs

@@ -12,53 +12,84 @@ namespace StansAssets.Foundation.Async
     /// </summary>
     public class MonoBehaviourCallback : MonoSingleton<MonoBehaviourCallback>
     {
+        event Action m_OnUpdate = delegate { };
+        event Action m_OnLateUpdate = delegate { };
+        event Action m_OnFixedUpdate = delegate { };
+        event Action m_OnApplicationQuit = delegate { };
+        event Action<bool> m_ApplicationOnPause = delegate { };
+        event Action<bool> m_OnApplicationFocus = delegate { };
+
         /// <summary>
         /// Update is called every frame.
         /// Learn more: [MonoBehaviour.Update](https://docs.unity3d.com/ScriptReference/MonoBehaviour.Update.html)
         /// </summary>
-        public static event Action OnUpdate;
+        public static event Action OnUpdate
+        {
+            add => Instance.m_OnUpdate += value;
+            remove => Instance.m_OnUpdate -= value;
+        }
 
         /// <summary>
         /// LateUpdate is called after all Update functions have been called. This is useful to order script execution.
         /// For example a follow camera should always be implemented in LateUpdate because it tracks objects that might have moved inside Update.
         /// Learn more: [MonoBehaviour.LateUpdate](https://docs.unity3d.com/ScriptReference/MonoBehaviour.LateUpdate.html)
         /// </summary>
-        public static event Action OnLateUpdate;
+        public static event Action OnLateUpdate
+        {
+            add => Instance.m_OnLateUpdate += value;
+            remove => Instance.m_OnLateUpdate -= value;
+        }
+
+        /// <summary>
+        /// Frame-rate independent MonoBehaviour.FixedUpdate message for physics calculations.
+        /// Learn more: [MonoBehaviour.FixedUpdate](https://docs.unity3d.com/ScriptReference/MonoBehaviour.FixedUpdate.html)
+        /// </summary>
+        public static event Action OnFixedUpdate
+        {
+            add => Instance.m_OnFixedUpdate += value;
+            remove => Instance.m_OnFixedUpdate -= value;
+        }
 
         /// <summary>
         /// In the editor this is called when the user stops playmode.
         /// Learn more: [MonoBehaviour.OnApplicationQuit](https://docs.unity3d.com/ScriptReference/MonoBehaviour.OnApplicationQuit.html)
         /// </summary>
-        public static event Action ApplicationOnQuit;
+        public static event Action ApplicationOnQuit
+        {
+            add => Instance.m_OnApplicationQuit += value;
+            remove => Instance.m_OnApplicationQuit -= value;
+        }
 
         /// <summary>
         /// Sent to all GameObjects when the application pauses.
         /// Learn more: [MonoBehaviour.OnApplicationPause](https://docs.unity3d.com/ScriptReference/MonoBehaviour.OnApplicationPause.html)
         /// </summary>
-        public static event Action<bool> ApplicationOnPause;
+        public static event Action<bool> ApplicationOnPause
+        {
+            add => Instance.m_ApplicationOnPause += value;
+            remove => Instance.m_ApplicationOnPause -= value;
+        }
 
         /// <summary>
         /// Sent to all GameObjects when the player gets or loses focus.
         /// Learn more: [MonoBehaviour.OnApplicationFocus](https://docs.unity3d.com/ScriptReference/MonoBehaviour.OnApplicationFocus.html)
         /// </summary>
-        public static event Action<bool> ApplicationOnFocus;
-
-        /// <summary>
-        /// Frame-rate independent MonoBehaviour.FixedUpdate message for physics calculations.
-        /// Learn more: [MonoBehaviour.FixedUpdate](https://docs.unity3d.com/ScriptReference/MonoBehaviour.FixedUpdate.html)
-        /// </summary>
-        public static event Action OnFixedUpdate;
+        public static event Action<bool> ApplicationOnFocus
+        {
+            add => Instance.m_OnApplicationFocus += value;
+            remove => Instance.m_OnApplicationFocus -= value;
+        }
 
-        void Update() => OnUpdate?.Invoke();
-        void LateUpdate() => OnLateUpdate?.Invoke();
-        void FixedUpdate() => OnFixedUpdate?.Invoke();
-        void OnApplicationPause(bool pauseStatus) => ApplicationOnPause?.Invoke(pauseStatus);
-        void OnApplicationFocus(bool hasFocus) => ApplicationOnFocus?.Invoke(hasFocus);
+        void Update() => m_OnUpdate.Invoke();
+        void LateUpdate() => m_OnLateUpdate.Invoke();
+        void FixedUpdate() => m_OnFixedUpdate.Invoke();
+        void OnApplicationPause(bool pauseStatus) => m_ApplicationOnPause.Invoke(pauseStatus);
+        void OnApplicationFocus(bool hasFocus) => m_OnApplicationFocus.Invoke(hasFocus);
 
         protected override void OnApplicationQuit()
         {
             base.OnApplicationQuit();
-            ApplicationOnQuit?.Invoke();
+            m_OnApplicationQuit.Invoke();
         }
     }
 }

Runtime/Async/MainThreadDispatcher/MainThreadDispatcherRuntime.cs

@@ -4,7 +4,6 @@ class MainThreadDispatcherRuntime : MainThreadDispatcherBase
     {
         public override void Init()
         {
-            MonoBehaviourCallback.Instantiate();
             MonoBehaviourCallback.OnUpdate += Update;
         }
     }

Runtime/Patterns/Singleton/MonoSingleton.cs

@@ -55,8 +55,14 @@ public static T Instance
         /// But it may be useful if you want manually control when the instance is created,
         /// even if you do not this specific instance at the moment
         /// </summary>
-        public static void Instantiate()
+        static void Instantiate()
         {
+            if (HasInstance)
+            {
+                Debug.LogWarning($"You are trying to Instantiate {typeof(T).FullName}, but it already has an Instance. Please use Instance property instead.");
+                return;
+            }
+
             var name = typeof(T).FullName;
             s_Instance = new GameObject(name).AddComponent<T>();
         }

Tests/Editor/Patterns/MonoSingletonTests.cs

@@ -0,0 +1,28 @@
+using System;
+using NUnit.Framework;
+using StansAssets.Foundation.Patterns;
+
+namespace StansAssets.Foundation.Tests.Patterns
+{
+    class TestSingleton : MonoSingleton<TestSingleton>
+    {
+        public readonly string Id;
+
+        public TestSingleton()
+        {
+            Id = Guid.NewGuid().ToString();
+        }
+    }
+
+    public class MonoSingletonTests
+    {
+        [Test]
+        public void SingleInstanceTest()
+        {
+            var a = TestSingleton.Instance;
+            var b = TestSingleton.Instance;
+            var c = TestSingleton.Instance;
+            Assert.IsTrue(a.Id.Equals(b.Id) && b.Id.Equals(c.Id));
+        }
+    }
+}

package.json

@@ -1,7 +1,7 @@
 {
   "name": "com.stansassets.foundation",
   "displayName": "Stans Assets - Foundation",
-  "version": "1.0.27",
+  "version": "2.0.0",
   "unity": "2018.4",
   "description": "Foundation package is a collection of utility methods, design patterns, and extensions for Unity.",
   "keywords": [