PHP7 Mediator

Author: Dominik Liebler

Behavioral/Mediator/Colleague.php

@@ -4,7 +4,7 @@
 
 /**
  * Colleague is an abstract colleague who works together but he only knows
- * the Mediator, not other colleague.
+ * the Mediator, not other colleagues
  */
 abstract class Colleague
 {
@@ -13,21 +13,13 @@ abstract class Colleague
      *
      * @var MediatorInterface
      */
-    private $mediator;
+    protected $mediator;
 
     /**
-     * @param MediatorInterface $medium
+     * @param MediatorInterface $mediator
      */
-    public function __construct(MediatorInterface $medium)
+    public function setMediator(MediatorInterface $mediator)
     {
-        // in this way, we are sure the concrete colleague knows the mediator
-        $this->mediator = $medium;
-    }
-
-    // for subclasses
-
-    protected function getMediator()
-    {
-        return $this->mediator;
+        $this->mediator = $mediator;
     }
 }

Behavioral/Mediator/Mediator.php

@@ -3,59 +3,54 @@
 namespace DesignPatterns\Behavioral\Mediator;
 
 /**
- * Mediator is the concrete Mediator for this design pattern.
- * In this example, I have made a "Hello World" with the Mediator Pattern.
+ * Mediator is the concrete Mediator for this design pattern
+ *
+ * In this example, I have made a "Hello World" with the Mediator Pattern
  */
 class Mediator implements MediatorInterface
 {
     /**
      * @var Subsystem\Server
      */
-    protected $server;
+    private $server;
 
     /**
      * @var Subsystem\Database
      */
-    protected $database;
+    private $database;
 
     /**
      * @var Subsystem\Client
      */
-    protected $client;
+    private $client;
 
     /**
-     * @param Subsystem\Database $db
-     * @param Subsystem\Client   $cl
-     * @param Subsystem\Server   $srv
+     * @param Subsystem\Database $database
+     * @param Subsystem\Client $client
+     * @param Subsystem\Server $server
      */
-    public function setColleague(Subsystem\Database $db, Subsystem\Client $cl, Subsystem\Server $srv)
+    public function __construct(Subsystem\Database $database, Subsystem\Client $client, Subsystem\Server $server)
     {
-        $this->database = $db;
-        $this->server = $srv;
-        $this->client = $cl;
+        $this->database = $database;
+        $this->server = $server;
+        $this->client = $client;
+
+        $this->database->setMediator($this);
+        $this->server->setMediator($this);
+        $this->client->setMediator($this);
     }
 
-    /**
-     * make request.
-     */
     public function makeRequest()
     {
         $this->server->process();
     }
 
-    /**
-     * query db.
-     *
-     * @return mixed
-     */
-    public function queryDb()
+    public function queryDb(): string
     {
         return $this->database->getData();
     }
 
     /**
-     * send response.
-     *
      * @param string $content
      */
     public function sendResponse($content)

Behavioral/Mediator/MediatorInterface.php

@@ -4,7 +4,7 @@
 
 /**
  * MediatorInterface is a contract for the Mediator
- * This interface is not mandatory but it is better for LSP concerns.
+ * This interface is not mandatory but it is better for Liskov substitution principle concerns.
  */
 interface MediatorInterface
 {
@@ -16,12 +16,12 @@ interface MediatorInterface
     public function sendResponse($content);
 
     /**
-     * makes a request.
+     * makes a request
      */
     public function makeRequest();
 
     /**
-     * queries the DB.
+     * queries the DB
      */
     public function queryDb();
 }

Behavioral/Mediator/Subsystem/Client.php

@@ -5,24 +5,16 @@
 use DesignPatterns\Behavioral\Mediator\Colleague;
 
 /**
- * Client is a client that make request et get response.
+ * Client is a client that makes requests and gets the response response.
  */
 class Client extends Colleague
 {
-    /**
-     * request.
-     */
     public function request()
     {
-        $this->getMediator()->makeRequest();
+        $this->mediator->makeRequest();
     }
 
-    /**
-     * output content.
-     *
-     * @param string $content
-     */
-    public function output($content)
+    public function output(string $content)
     {
         echo $content;
     }

Behavioral/Mediator/Subsystem/Database.php

@@ -4,15 +4,9 @@
 
 use DesignPatterns\Behavioral\Mediator\Colleague;
 
-/**
- * Database is a database service.
- */
 class Database extends Colleague
 {
-    /**
-     * @return string
-     */
-    public function getData()
+    public function getData(): string
     {
         return 'World';
     }

Behavioral/Mediator/Subsystem/Server.php

@@ -4,17 +4,11 @@
 
 use DesignPatterns\Behavioral\Mediator\Colleague;
 
-/**
- * Server serves responses.
- */
 class Server extends Colleague
 {
-    /**
-     * process on server.
-     */
     public function process()
     {
-        $data = $this->getMediator()->queryDb();
-        $this->getMediator()->sendResponse("Hello $data");
+        $data = $this->mediator->queryDb();
+        $this->mediator->sendResponse(sprintf("Hello %s", $data));
     }
 }

Behavioral/Mediator/Tests/MediatorTest.php

@@ -7,27 +7,14 @@
 use DesignPatterns\Behavioral\Mediator\Subsystem\Database;
 use DesignPatterns\Behavioral\Mediator\Subsystem\Server;
 
-/**
- * MediatorTest tests hello world.
- */
 class MediatorTest extends \PHPUnit_Framework_TestCase
 {
-    protected $client;
-
-    protected function setUp()
-    {
-        $media = new Mediator();
-        $this->client = new Client($media);
-        $media->setColleague(new Database($media), $this->client, new Server($media));
-    }
-
     public function testOutputHelloWorld()
     {
-        // testing if Hello World is output :
+        $client = new Client();
+        new Mediator(new Database(), $client, new Server());
+
         $this->expectOutputString('Hello World');
-        // as you see, the 3 components Client, Server and Database are totally decoupled
-        $this->client->request();
-        // Anyway, it remains complexity in the Mediator that's why the pattern
-        // Observer is preferable in mnay situations.
+        $client->request();
     }
 }