Implement InversionOfControl aware DependencyInjection

DependencyInjection/AbstractConfig.php

@@ -0,0 +1,19 @@
+<?php
+
+namespace DesignPatterns\DependencyInjection;
+
+/**
+ * class AbstractConfig
+ */
+abstract class AbstractConfig implements Parameters
+{
+    /**
+     * @var Storage of data
+     */
+    protected $storage;
+
+    public function __construct($storage)
+    {
+        $this->storage = $storage;
+    }
+}

DependencyInjection/ArrayConfig.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace DesignPatterns\DependencyInjection;
+
+/**
+ * class ArrayConfig
+ *
+ * uses array as data source
+ */
+class ArrayConfig extends AbstractConfig
+{
+    /**
+     * Get parameter
+     *
+     * @param string|int $key
+     * 
+     * @return mixed
+     */
+    public function get($key, $default = null) {;
+        if (isset($this->storage[$key])) {
+            return $this->storage[$key];
+        }
+        return $default;
+    }
+
+    /**
+     * Set parameter
+     *
+     * @param string|int $key
+     * @param mixed      $value
+     */
+    public function set($key, $value)
+    {
+        $this->storage[$key] = $value;
+    }
+}

DependencyInjection/Configuration.php

@@ -1,34 +0,0 @@
-<?php
-
-namespace DesignPatterns\DependencyInjection;
-
-/**
- * class Configuration
- */
-class Configuration
-{
-    /**
-     * @var string
-     */
-    protected $host;
-
-    /**
-     * @param string $host
-     *
-     * @return Configuration
-     */
-    public function setHost($host)
-    {
-        $this->host = $host;
-
-        return $this; // for a fluent interface
-    }
-
-    /**
-     * @return string
-     */
-    public function getHost()
-    {
-        return $this->host;
-    }
-}

DependencyInjection/Connection.php

@@ -13,13 +13,23 @@ class Connection
     protected $configuration;
 
     /**
-     * here, Configuration gets injected and Connection will get all that it needs from Configuration
-     * without DI, the configuration would be created directly in Connection, which is not very good
+     * @var Currently connected host
+     */
+    protected $host;
+
+    /**
+     * Here, Configuration gets injected and Connection will get all that it needs from Configuration
+     * Without DI, the configuration would be created directly in Connection, which is not very good
      * for testing and extending Connection
      *
-     * @param Configuration $config
+     * Notice we are following Inversion of control principle here by asking Config to implement
+     * Parameters interface. This decouples our components. We don't care where the sorce of information,
+     * we only care that config has certain methods to retrieve that information. Read more about Inversion
+     * of control <http://en.wikipedia.org/wiki/Inversion_of_control>
+     *
+     * @param Parameters $config
      */
-    public function __construct(Configuration $config)
+    public function __construct(Parameters $config)
     {
         $this->configuration = $config;
     }
@@ -29,7 +39,20 @@ class Connection
      */
     public function connect()
     {
-        $host = $this->configuration->getHost();
-        // ...
+        $host = $this->configuration->get('host');
+        // connection to host, authentication etc...
+
+        //if connected
+        $this->host = $host;
+    }
+
+    /*
+     * Get currently connected host
+     *
+     * @return string
+     */
+    public function getHost()
+    {
+        return $this->host;
     }
 }

DependencyInjection/Parameters.php

@@ -0,0 +1,26 @@
+<?php
+
+namespace DesignPatterns\DependencyInjection;
+
+/**
+ * Parameters interface
+ */
+interface Parameters 
+{
+    /**
+     * Get parameter
+     *
+     * @param string|int $key
+     * 
+     * @return mixed
+     */
+    public function get($key);
+
+    /**
+     * Set parameter
+     *
+     * @param string|int $key
+     * @param mixed      $value
+     */
+    public function set($key, $value);
+}

Tests/DependencyInjection/DependencyInjectionTest.php

@@ -0,0 +1,27 @@
+<?php
+
+namespace DesignPatterns\Tests\DependencyInjection;
+
+use DesignPatterns\DependencyInjection\Parameters;
+use DesignPatterns\DependencyInjection\AbstractConfig;
+use DesignPatterns\DependencyInjection\ArrayConfig;
+use DesignPatterns\DependencyInjection\Connection;
+
+class DependencyInjectionTest extends \PHPUnit_Framework_TestCase
+{
+    protected $config;
+    protected $source;
+
+    public function setUp()
+    {
+        $this->source = include 'config.php';
+        $this->config = new ArrayConfig($this->source);
+    }
+
+    public function testDependencyInjection()
+    {
+        $connection = new Connection($this->config);
+        $connection->connect();
+        $this->assertEquals($this->source['host'], $connection->getHost());
+    }
+}

Tests/DependencyInjection/config.php

@@ -0,0 +1,3 @@
+<?php
+
+return array('host' => 'github.com');