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Added Service Locator pattern
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‎ServiceLocator/DatabaseService.php‎

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

‎ServiceLocator/DatabaseServiceInterface.php‎

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

‎ServiceLocator/LogService.php‎

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

‎ServiceLocator/LogServiceInterface.php‎

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

‎ServiceLocator/README.md‎

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# Service Locator
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## Purpose
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To implement a loosely coupled architecture in order to get better testable, maintainable and extendable code.
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DI pattern and Service Locator pattern are an implementation of the Inverse of Control pattern.
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## Usage
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With `ServiceLocator` you can register a service for a given interface. By using the interface you can retrieve the service
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and use it in the classes of the application without knowing its implementation. You can configure and inject the
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Service Locator object on bootstrap.
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## Examples
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* 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
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namespace DesignPatterns\ServiceLocator;
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class ServiceLocator implements ServiceLocatorInterface
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{
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/**
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* All services.
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*
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* @var array
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*/
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private $services;
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/**
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* The services which have an instance.
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*
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* @var array
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*/
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private $instantiated;
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/**
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* True if a service can be shared.
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*
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* @var array
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*/
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private $shared;
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public function __construct()
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{
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$this->services = array();
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$this->instantiated = array();
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$this->shared = array();
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}
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/**
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* Registers a service with specific interface.
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*
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* @param string $interface
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* @param string|object $service
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* @param bool $share
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*/
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public function add($interface, $service, $share = true)
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{
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/**
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* When you add a service, you should register it
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* with its interface or with a string that you can use
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* in the future even if you will change the service implementation.
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*/
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if(is_object($service) && $share)
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$this->instantiated[$interface] = $service;
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$this->services[$interface] = (is_object($service) ? get_class($service) : $service);
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$this->shared[$interface] = $share;
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}
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/**
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* Checks if a service is registered.
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*
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* @param string $interface
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*
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* @return bool
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*/
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public function has($interface)
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{
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return (isset($this->services[$interface]) || isset($this->instantiated[$interface]));
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}
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/**
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* Gets the service registered for the interface.
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*
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* @param string $interface
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*
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* @return mixed
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*/
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public function get($interface)
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{
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// Retrieves the instance if it exists and it is shared
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if(isset($this->instantiated[$interface]) && $this->shared[$interface])
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return $this->instantiated[$interface];
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// otherwise gets the service registered.
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$service = $this->services[$interface];
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// You should check if the service class exists and
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// the class is instantiable.
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// This example is a simple implementation, but
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// when you create a service, you can decide
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// if $service is a factory or a class.
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// By registering a factory you can create your services
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// using the DependencyInjection pattern.
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// ...
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// Creates the service object
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$object = new $service();
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// and saves it if the service must be shared.
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if($this->shared[$interface])
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$this->instantiated[$interface] = $object;
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return $object;
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}
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}

‎ServiceLocator/ServiceLocatorInterface.php‎

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

‎Tests/ServiceLocator/ServiceLocatorTest.php‎

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