Prevent AddListener from adding the same delegate

We found that ensuring that delegate instances are unique was a good way to prevent odd, difficult to detect behavior. This behavior is present to some extent in BaseSignal, so it seems to make sense to add it to Signal's implementation as well.
BryceQi · May 5, 2014 · 3bad4a8 · 3bad4a8
1 parent 6a0cc3f
commit 3bad4a8
Show file tree

Hide file tree

Showing 2 changed files with 146 additions and 7 deletions.
diff --git a/StrangeIoC/scripts/strange/.tests/extensions/signal/TestSignal.cs b/StrangeIoC/scripts/strange/.tests/extensions/signal/TestSignal.cs
@@ -137,6 +137,107 @@ public void TestMultipleCallbacks()
             Assert.AreEqual(testInt + 1, testValue);
         }
 
+        [Test]
+        public void AddListener_SignalWithNoTypeGivenSameCallbackMultipleTimes_ExpectsDelegateCalledOnlyOnce()
+        {
+            Signal signal = new Signal();
+            simpleInt = 0;
+
+            signal.AddListener(SimpleSignalCallback);
+            signal.AddListener(SimpleSignalCallback);
+
+            signal.Dispatch();
+
+            Assert.AreEqual(1, simpleInt);
+        }
+
+        private int simpleInt;
+        private void SimpleSignalCallback()
+        {
+            simpleInt++;
+        }
+
+        [Test]
+        public void AddListener_SignalWithOneTypeGivenSameCallbackMultipleTimes_ExpectsDelegateCalledOnlyOnce()
+        {
+            Signal<int> signal = new Signal<int>();
+            simpleInt = 1;
+
+            signal.AddListener(OneArgSignalCallback);
+            signal.AddListener(OneArgSignalCallback);
+
+            signal.Dispatch(simpleInt);
+
+            Assert.AreEqual(1, testValue);
+        }
+
+        [Test]
+        public void AddListener_SignalWithTwoTypesGivenSameCallbackMultipleTimes_ExpectsDelegateCalledOnlyOnce()
+        {
+            Signal<int,int> signal = new Signal<int,int>();
+            int firstInt = 1;
+            int secondInt = 2;
+
+            signal.AddListener(TwoArgCallback);
+            signal.AddListener(TwoArgCallback);
+
+            signal.Dispatch(firstInt, secondInt);
+            int expected = firstInt + secondInt;
+            Assert.AreEqual(expected, this.testValue);
+        }
+
+        private void TwoArgCallback(int arg1, int arg2)
+        {
+            this.testValue += arg1 + arg2;
+        }
+
+        [Test]
+        public void AddListener_SignalWithThreeTypesGivenSameCallbackMultipleTimes_ExpectsDelegateCalledOnlyOnce()
+        {
+            Signal<int,int,int> signal = new Signal<int, int, int>();
+            int firstInt = 1;
+            int secondInt = 2;
+            int thirdInt = 3;
+
+            signal.AddListener(ThreeArgCallback);
+            signal.AddListener(ThreeArgCallback);
+
+            signal.Dispatch(firstInt, secondInt, thirdInt);
+            int expected = firstInt + secondInt + thirdInt;
+
+            Assert.AreEqual(expected, this.testValue);
+
+        }
+
+        private void ThreeArgCallback(int arg1, int arg2, int arg3)
+        {
+            this.testValue += arg1 + arg2 + arg3;
+        }
+
+        [Test]
+        public void AddListener_SignalWithFourTypesGivenSameCallbackMultipleTimes_ExpectsDelegateCalledOnlyOnce()
+        {
+            Signal<int, int, int, int> signal = new Signal<int, int, int, int>();
+            int firstInt = 1;
+            int secondInt = 2;
+            int thirdInt = 3;
+            int fourthInt = 4;
+
+            signal.AddListener(FourArgCallback);
+            signal.AddListener(FourArgCallback);
+
+            signal.Dispatch(firstInt, secondInt, thirdInt, fourthInt);
+            int expected = firstInt + secondInt + thirdInt + fourthInt;
+
+            Assert.AreEqual(expected, this.testValue);
+
+        }
+
+        private void FourArgCallback(int arg1, int arg2, int arg3, int arg4)
+        {
+            this.testValue += arg1 + arg2 + arg3 + arg4;
+        }
+
         [Test]
         public void TestRemoveListener()
         {

diff --git a/StrangeIoC/scripts/strange/extensions/signal/impl/Signal.cs b/StrangeIoC/scripts/strange/extensions/signal/impl/Signal.cs
@@ -65,7 +65,9 @@
  */
 
 using System;
+using System.Collections;
 using System.Collections.Generic;
+using System.Linq;
 
 namespace strange.extensions.signal.impl
 {
@@ -74,8 +76,16 @@ public class Signal : BaseSignal
 	{
 		public event Action Listener = delegate { };
 		public event Action OnceListener = delegate { };
-		public void AddListener(Action callback) { Listener += callback; }
-		public void AddOnce(Action callback) { OnceListener += callback; }
+
+	    public void AddListener(Action callback)
+	    {
+            if (!Listener.GetInvocationList().Contains(callback))
+            {
+                Listener += callback;
+            }
+	    }
+
+	    public void AddOnce(Action callback) { OnceListener += callback; }
 		public void RemoveListener(Action callback) { Listener -= callback; }
 		public override List<Type> GetTypes()
 		{
@@ -94,8 +104,15 @@ public void Dispatch()
 	public class Signal<T> : BaseSignal
 	{
 		public event Action<T> Listener = delegate { };
-		public event Action<T> OnceListener = delegate { };
-		public void AddListener(Action<T> callback) { Listener += callback; }
+		public event Action<T> OnceListener = delegate { };	    
+
+	    public void AddListener(Action<T> callback)
+	    {
+	        if (!Listener.GetInvocationList().Contains(callback))
+	        {
+	            Listener += callback;
+	        }
+	    }
 		public void AddOnce(Action<T> callback) { OnceListener += callback; }
 		public void RemoveListener(Action<T> callback) { Listener -= callback; }
 		public override  List<Type> GetTypes() 
@@ -119,7 +136,14 @@ public class Signal<T, U> : BaseSignal
 	{
 		public event Action<T, U> Listener = delegate { };
 		public event Action<T, U> OnceListener = delegate { };
-		public void AddListener(Action<T, U> callback) { Listener += callback; }
+
+	    public void AddListener(Action<T, U> callback)
+	    {
+            if (!Listener.GetInvocationList().Contains(callback))
+            {
+                Listener += callback;
+            }
+        }
 		public void AddOnce(Action<T, U> callback) { OnceListener += callback; }
 		public void RemoveListener(Action<T, U> callback) { Listener -= callback; }
 		public override List<Type> GetTypes()
@@ -144,7 +168,14 @@ public class Signal<T, U, V> : BaseSignal
 	{
 		public event Action<T, U, V> Listener = delegate { };
 		public event Action<T, U, V> OnceListener = delegate { };
-		public void AddListener(Action<T, U, V> callback) { Listener += callback; }
+
+	    public void AddListener(Action<T, U, V> callback)
+	    {
+            if (!Listener.GetInvocationList().Contains(callback))
+            {
+                Listener += callback;
+            }
+	    }
 		public void AddOnce(Action<T, U, V> callback) { OnceListener += callback; }
 		public void RemoveListener(Action<T, U, V> callback) { Listener -= callback; }
 		public override List<Type> GetTypes()
@@ -170,7 +201,14 @@ public class Signal<T, U, V, W> : BaseSignal
 	{
 		public event Action<T, U, V, W> Listener = delegate { };
 		public event Action<T, U, V, W> OnceListener = delegate { };
-		public void AddListener(Action<T, U, V, W> callback) { Listener += callback; }
+
+	    public void AddListener(Action<T, U, V, W> callback)
+	    {
+            if (!Listener.GetInvocationList().Contains(callback))
+            {
+                Listener += callback;
+            }
+	    }
 		public void AddOnce(Action<T, U, V, W> callback) { OnceListener += callback; }
 		public void RemoveListener(Action<T, U, V, W> callback) { Listener -= callback; }
 		public override List<Type> GetTypes()