Merge pull request Habrador#6 from masoudarvishian/implement_command_queue

Implementation of the Command Queue (Event Queue) pattern is added.

Author: Habrador

Assets/Patterns/14. Command Queue (Event Queue).meta

@@ -0,0 +1,57 @@
+using System.Collections.Generic;
+
+namespace CommandQueuePattern
+{
+    public class CommandQueue 
+    {
+        // queue of commands
+        private readonly Queue<ICommand> _queue;
+
+        // it's true when a command is running
+        private bool _isPending;
+
+        public CommandQueue()
+        {
+            // create a queue
+            _queue = new Queue<ICommand>();
+
+            // no command is running
+            _isPending = false;
+        }
+
+        public void Enqueue(ICommand cmd)
+        {
+            // add a command
+            _queue.Enqueue(cmd);
+
+            // if no command is running, start to execute commands
+            if (!_isPending)
+                DoNext();
+        }
+
+        public void DoNext()
+        {
+            // if queue is empty, do nothing.
+            if (_queue.Count == 0)
+                return;
+
+            // get a command
+            var cmd = _queue.Dequeue();
+            // setting _isPending to true means this command is running
+            _isPending = true;
+            // listen to the OnFinished event
+            cmd.OnFinished += OnCmdFinished;
+            // execute command
+            cmd.Execute();
+        }
+
+        private void OnCmdFinished()
+        {
+            // current command is finished
+            _isPending = false;
+
+            // run the next command
+            DoNext();
+        }
+    }
+}