88 - Added undo example for command pattern

Author: andrewnester

Behavioral/Command/AddMessageDateCommand.php

@@ -0,0 +1,46 @@
+<?php
+
+namespace DesignPatterns\Behavioral\Command;
+
+/**
+ * This concrete command tweaks receiver to add current date to messages
+ * invoker just knows that it can call "execute".
+ */
+class AddMessageDateCommand implements CommandInterface, UndoableCommandInterface
+{
+    /**
+     * @var Receiver
+     */
+    protected $output;
+
+    /**
+     * Each concrete command is built with different receivers.
+     * There can be one, many or completely no receivers, but there can be other commands in the parameters.
+     *
+     * @param Receiver $console
+     */
+    public function __construct(Receiver $console)
+    {
+        $this->output = $console;
+    }
+
+    /**
+     * Execute and make receiver to enable displaying messages date.
+     */
+    public function execute()
+    {
+        // sometimes, there is no receiver and this is the command which
+        // does all the work
+        $this->output->enableDate();
+    }
+
+    /**
+     * Undo the command and make receiver to disable displaying messages date.
+     */
+    public function undo()
+    {
+        // sometimes, there is no receiver and this is the command which
+        // does all the work
+        $this->output->disableDate();
+    }
+}

Behavioral/Command/Receiver.php

@@ -7,11 +7,40 @@
  */
 class Receiver
 {
+    private $enableDate = false;
+
+    private $output = array();
+
     /**
      * @param string $str
      */
     public function write($str)
     {
-        echo $str;
+        if ($this->enableDate) {
+            $str .= ' ['.date('Y-m-d').']';
+        }
+
+        $this->output[] = $str;
+    }
+
+    public function getOutput()
+    {
+        return implode("\n", $this->output);
+    }
+
+    /**
+     * Enable receiver to display message date.
+     */
+    public function enableDate()
+    {
+        $this->enableDate = true;
+    }
+
+    /**
+     * Disable receiver to display message date.
+     */
+    public function disableDate()
+    {
+        $this->enableDate = false;
     }
 }

Behavioral/Command/Tests/CommandTest.php

@@ -30,7 +30,7 @@ protected function setUp()
     public function testInvocation()
     {
         $this->invoker->setCommand(new HelloCommand($this->receiver));
-        $this->expectOutputString('Hello World');
         $this->invoker->run();
+        $this->assertEquals($this->receiver->getOutput(), 'Hello World');
     }
 }

Behavioral/Command/Tests/UndoableCommandTest.php

@@ -0,0 +1,49 @@
+<?php
+
+namespace DesignPatterns\Behavioral\Command\Tests;
+
+use DesignPatterns\Behavioral\Command\AddMessageDateCommand;
+use DesignPatterns\Behavioral\Command\HelloCommand;
+use DesignPatterns\Behavioral\Command\Invoker;
+use DesignPatterns\Behavioral\Command\Receiver;
+use PHPUnit_Framework_TestCase;
+
+/**
+ * UndoableCommandTest has the role of the Client in the Command Pattern.
+ */
+class UndoableCommandTest extends PHPUnit_Framework_TestCase
+{
+    /**
+     * @var Invoker
+     */
+    protected $invoker;
+
+    /**
+     * @var Receiver
+     */
+    protected $receiver;
+
+    protected function setUp()
+    {
+        $this->invoker = new Invoker();
+        $this->receiver = new Receiver();
+    }
+
+    public function testInvocation()
+    {
+        $this->invoker->setCommand(new HelloCommand($this->receiver));
+        $this->invoker->run();
+        $this->assertEquals($this->receiver->getOutput(), 'Hello World');
+
+        $messageDateCommand = new AddMessageDateCommand($this->receiver);
+        $messageDateCommand->execute();
+
+        $this->invoker->run();
+        $this->assertEquals($this->receiver->getOutput(), "Hello World\nHello World [".date('Y-m-d').']');
+
+        $messageDateCommand->undo();
+
+        $this->invoker->run();
+        $this->assertEquals($this->receiver->getOutput(), "Hello World\nHello World [".date('Y-m-d')."]\nHello World");
+    }
+}

Behavioral/Command/UndoableCommandInterface.php

@@ -0,0 +1,15 @@
+<?php
+
+namespace DesignPatterns\Behavioral\Command;
+
+/**
+ * Interface UndoableCommandInterface.
+ */
+interface UndoableCommandInterface
+{
+    /**
+     * This method is used to undo change made by command execution
+     * The Receiver goes in the constructor.
+     */
+    public function undo();
+}