Added Service Locator pattern

ServiceLocator/DatabaseService.php

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+<?php
+
+namespace DesignPatterns\ServiceLocator;
+
+class DatabaseService implements DatabaseServiceInterface
+{
+
+} 

ServiceLocator/DatabaseServiceInterface.php

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+<?php
+
+namespace DesignPatterns\ServiceLocator;
+
+interface DatabaseServiceInterface
+{
+
+} 

ServiceLocator/LogService.php

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+<?php
+
+namespace DesignPatterns\ServiceLocator;
+
+class LogService implements LogServiceInterface
+{
+
+} 

ServiceLocator/LogServiceInterface.php

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+<?php
+
+namespace DesignPatterns\ServiceLocator;
+
+interface LogServiceInterface
+{
+
+} 

ServiceLocator/README.md

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+# Service Locator
+
+## Purpose
+
+To implement a loosely coupled architecture in order to get better testable, maintainable and extendable code.
+DI pattern and Service Locator pattern are an implementation of the Inverse of Control pattern.
+
+## Usage
+
+With `ServiceLocator` you can register a service for a given interface. By using the interface you can retrieve the service
+and use it in the classes of the application without knowing its implementation. You can configure and inject the
+Service Locator object on bootstrap.
+
+## Examples
+
+* Zend Framework 2 uses Service Locator to create and share services used in the framework(i.e. EventManager, ModuleManager, all custom user services provided by modules, etc...)

ServiceLocator/ServiceLocator.php

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+<?php
+
+namespace DesignPatterns\ServiceLocator;
+
+class ServiceLocator implements ServiceLocatorInterface
+{
+    /**
+     * All services.
+     *
+     * @var array
+     */
+    private $services;
+
+    /**
+     * The services which have an instance.
+     *
+     * @var array
+     */
+    private $instantiated;
+
+    /**
+     * True if a service can be shared.
+     *
+     * @var array
+     */
+    private $shared;
+
+    public function __construct()
+    {
+        $this->services = array();
+        $this->instantiated = array();
+        $this->shared = array();
+    }
+
+    /**
+     * Registers a service with specific interface.
+     *
+     * @param string        $interface
+     * @param string|object $service
+     * @param bool          $share
+     */
+    public function add($interface, $service, $share = true)
+    {
+        /**
+         * When you add a service, you should register it
+         * with its interface or with a string that you can use
+         * in the future even if you will change the service implementation.
+         */
+
+        if(is_object($service) && $share)
+            $this->instantiated[$interface] = $service;
+
+        $this->services[$interface] = (is_object($service) ? get_class($service) : $service);
+        $this->shared[$interface] = $share;
+    }
+
+    /**
+     * Checks if a service is registered.
+     *
+     * @param string $interface
+     *
+     * @return bool
+     */
+    public function has($interface)
+    {
+        return (isset($this->services[$interface]) || isset($this->instantiated[$interface]));
+    }
+
+    /**
+     * Gets the service registered for the interface.
+     *
+     * @param string $interface
+     *
+     * @return mixed
+     */
+    public function get($interface)
+    {
+        // Retrieves the instance if it exists and it is shared
+        if(isset($this->instantiated[$interface]) && $this->shared[$interface])
+            return $this->instantiated[$interface];
+
+        // otherwise gets the service registered.
+        $service = $this->services[$interface];
+
+        // You should check if the service class exists and
+        // the class is instantiable.
+
+        // This example is a simple implementation, but
+        // when you create a service, you can decide
+        // if $service is a factory or a class.
+        // By registering a factory you can create your services
+        // using the DependencyInjection pattern.
+
+        // ...
+
+        // Creates the service object
+        $object = new $service();
+
+        // and saves it if the service must be shared.
+        if($this->shared[$interface])
+            $this->instantiated[$interface] = $object;
+
+        return $object;
+    }
+} 

ServiceLocator/ServiceLocatorInterface.php

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+<?php
+
+namespace DesignPatterns\ServiceLocator;
+
+interface ServiceLocatorInterface 
+{
+    /**
+     * Checks if a service is registered.
+     *
+     * @param string $interface
+     *
+     * @return bool
+     */
+    public function has($interface);
+
+    /**
+     * Gets the service registered for the interface.
+     *
+     * @param string $interface
+     *
+     * @return mixed
+     */
+    public function get($interface);
+} 

Tests/ServiceLocator/ServiceLocatorTest.php

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+<?php
+/**
+ * DesignPatternsPHP
+ *
+ * Copyright (c) 2014 Matteo Tafani Alunno
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+namespace DesignPatterns\Tests\ServiceLocator;
+
+use DesignPatterns\ServiceLocator\DatabaseService;
+use DesignPatterns\ServiceLocator\LogService;
+use DesignPatterns\ServiceLocator\ServiceLocator;
+use \PHPUnit_Framework_TestCase as TestCase;
+
+class ServiceLocatorTest extends TestCase
+{
+    /**
+     * @var LogService
+     */
+    private $logService;
+
+    /**
+     * @var DatabaseService
+     */
+    private $databaseService;
+
+    /**
+     * @var ServiceLocator
+     */
+    private $serviceLocator;
+
+    public function setUp()
+    {
+        $this->serviceLocator = new ServiceLocator();
+
+        $this->logService = new LogService();
+        $this->databaseService = new DatabaseService();
+    }
+
+    public function testHasServices()
+    {
+        $this->serviceLocator->add('DesignPatterns\ServiceLocator\LogServiceInterface', $this->logService);
+        $this->serviceLocator->add('DesignPatterns\ServiceLocator\DatabaseServiceInterface', $this->databaseService);
+
+        $this->assertTrue($this->serviceLocator->has('DesignPatterns\ServiceLocator\LogServiceInterface'));
+        $this->assertTrue($this->serviceLocator->has('DesignPatterns\ServiceLocator\DatabaseServiceInterface'));
+
+        $this->assertFalse($this->serviceLocator->has('DesignPatterns\ServiceLocator\FakeServiceInterface'));
+    }
+
+    public function testServicesWithObject()
+    {
+        $this->serviceLocator->add('DesignPatterns\ServiceLocator\LogServiceInterface', $this->logService);
+        $this->serviceLocator->add('DesignPatterns\ServiceLocator\DatabaseServiceInterface', $this->databaseService);
+
+        $this->assertSame($this->logService, $this->serviceLocator->get('DesignPatterns\ServiceLocator\LogServiceInterface'));
+        $this->assertSame($this->databaseService, $this->serviceLocator->get('DesignPatterns\ServiceLocator\DatabaseServiceInterface'));
+    }
+
+    public function testServicesWithClass()
+    {
+        $this->serviceLocator->add('DesignPatterns\ServiceLocator\LogServiceInterface', get_class($this->logService));
+        $this->serviceLocator->add('DesignPatterns\ServiceLocator\DatabaseServiceInterface', get_class($this->databaseService));
+
+        $this->assertNotSame($this->logService, $this->serviceLocator->get('DesignPatterns\ServiceLocator\LogServiceInterface'));
+        $this->assertInstanceOf('DesignPatterns\ServiceLocator\LogServiceInterface', $this->serviceLocator->get('DesignPatterns\ServiceLocator\LogServiceInterface'));
+
+        $this->assertNotSame($this->databaseService, $this->serviceLocator->get('DesignPatterns\ServiceLocator\DatabaseServiceInterface'));
+        $this->assertInstanceOf('DesignPatterns\ServiceLocator\DatabaseServiceInterface', $this->serviceLocator->get('DesignPatterns\ServiceLocator\DatabaseServiceInterface'));
+    }
+
+    public function testServicesNotShared()
+    {
+        $this->serviceLocator->add('DesignPatterns\ServiceLocator\LogServiceInterface', $this->logService, false);
+        $this->serviceLocator->add('DesignPatterns\ServiceLocator\DatabaseServiceInterface', $this->databaseService, false);
+
+        $this->assertNotSame($this->logService, $this->serviceLocator->get('DesignPatterns\ServiceLocator\LogServiceInterface'));
+        $this->assertInstanceOf('DesignPatterns\ServiceLocator\LogServiceInterface', $this->serviceLocator->get('DesignPatterns\ServiceLocator\LogServiceInterface'));
+
+        $this->assertNotSame($this->databaseService, $this->serviceLocator->get('DesignPatterns\ServiceLocator\DatabaseServiceInterface'));
+        $this->assertInstanceOf('DesignPatterns\ServiceLocator\DatabaseServiceInterface', $this->serviceLocator->get('DesignPatterns\ServiceLocator\DatabaseServiceInterface'));
+    }
+}
+