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1 <!DOCTYPE html> 2 <html class="no-js" id="top"> 3 <head> 4 <title>ProxyManager - Null object</title> 5 6 <meta name="description" content="A proxyManager write in php" /> 7 <meta name="keywords" content="ProxyManager, proxy, manager, ocramius, Marco Pivetta, php, null object" /> 8 <meta name="viewport" content="width=device-width, initial-scale=1, minimum-scale=1" /> 9 <link href='http://fonts.googleapis.com/css?family=Source+Sans+Pro:200,300,400,600' rel='stylesheet' type='text/css'> 10 <link href="css/styles.css" rel="stylesheet" /> 11 <link rel="stylesheet" href="//cdnjs.cloudflare.com/ajax/libs/highlight.js/8.3/styles/default.min.css"> 12 <script src="//cdnjs.cloudflare.com/ajax/libs/highlight.js/8.3/highlight.min.js"></script> 13 <script>hljs.initHighlightingOnLoad();</script> 14 <link rel="shortcut icon" href="favicon.ico"> 15 </head> 16 <body> 17 18 <header class="site-header"> 19 <div class="container"> 20 <h1><a href="index.html"><img alt="ProxyManager" src="img/block.png" /></a></h1> 21 22 <nav class="main-nav" role="navigation"> 23 <ul> 24 <li><a href="https://github.com/Ocramius/ProxyManager" target="_blank">Github</a> 25 <div class="bcms-clearfix"></div> 26 </li> 27 </ul> 28 </nav> 29 </div> 30 </header> 31 <main role="main"> 32 <section class="component-content"> 33 34 <div class="component-demo" id="live-demo"> 35 <div class="container"> 36 <div class="main-wrapper" style="text-align: right"> 37 <iframe src="http://ghbtns.com/github-btn.html?user=ocramius&repo=ProxyManager&type=fork&count=true&size=large" 38 allowtransparency="true" frameborder="0" scrolling="0" width="310" height="40"></iframe> 39 40 <iframe src="http://ghbtns.com/github-btn.html?user=ocramius&repo=ProxyManager&type=watch&count=true&size=large" 41 allowtransparency="true" frameborder="0" scrolling="0" width="200" height="40"></iframe> 42 43 </div> 44 <div class="bcms-clearfix bcms-clearfix"></div> 45 </div> 46 </div> 47 <div class="component-info"> 48 <div class="container"> 49 <aside class="sidebar"> 50 <nav class="spy-nav"> 51 <ul> 52 <li><a href="index.html">Intro</a></li> 53 <li><a href="virtual-proxy.html">Virtual Proxy</a></li> 54 <li><a href="null-object.html">Null Objects</a></li> 55 <li><a href="ghost-object.html">Ghost Objects</a></li> 56 <li><a href="remote-object.html">Remote Object</a></li> 57 <li><a href="contributing.html">Contributing</a></li> 58 <li><a href="credits.html">Credits</a></li> 59 <li><a href="copyright.html">Copyright</a></li> 60 </ul> 61 </nav> 62 <div class="bcms-clearfix bcms-clearfix"></div> 63 <a class="btn btn-action btn-full download-component" 64 href="download.html">Download</a> 65 <div class="bcms-clearfix"></div> 66 </aside> 67 68 <div class="content"> 69 <div class="bcms-clearfix"></div> 70 <h3 class="section-title">Null Object Proxy</h3> 71 <p>A Null Object proxy is a <a href="http://en.wikipedia.org/wiki/Null_Object_pattern" target="_blank">null object pattern</a> implementation. The proxy factory creates a new object with defined neutral behavior based on an other object, class name or interface.</p> 72 <hr /> 73 74 <h3 class="section-title">What is null object proxy ?</h3> 75 76 <p>In your application, when you can't return the object related to the request, the consumer of the model must check for the return value and handle the failing condition gracefully, thus generating an explosion of conditionals throughout your code. Fortunately, this seemingly-tangled situation can be sorted out simply by creating a polymorphic implementation of the domain object, which would implement the same interface as the one of the object in question, only that its methods wouldn’t do anything, therefore offloading client code from doing repetitive checks for ugly null values when the operation is executed.</p> 77 78 <hr /> 79 80 <h3 class="section-title">Usage examples</h3> 81 82 <pre> 83 <code class="php"> 84 class UserMapper 85 { 86 private $adapter; 87 88 public function __construct(DatabaseAdapterInterface $adapter) { 89 $this->adapter = $adapter; 90 } 91 92 public function fetchById($id) { 93 $this->adapter->select("users", array("id" => $id)); 94 if (!$row = $this->adapter->fetch()) { 95 return null; 96 } 97 return $this->createUser($row); 98 } 99 100 private function createUser(array $row) { 101 $user = new Entity\User($row["name"], $row["email"]); 102 $user->setId($row["id"]); 103 return $user; 104 } 105 } 106 </code> 107 </pre> 108 109 <p>If you want to remove conditionals from client code, you need to have a version of the entity conforming to the corresponding interface. With the Null Object Proxy, you can build this object :</p> 110 111 <pre> 112 <code class="php"> 113 $factory = new \ProxyManager\Factory\NullObjectFactory(); 114 115 $nullUser = $factory->createProxy('Entity\User'); 116 117 var_dump($nullUser->getName()); // empty return 118 </code> 119 </pre> 120 121 <p>You can now return a valid entity :</p> 122 123 <pre> 124 <code class="php"> 125 class UserMapper 126 { 127 private $adapter; 128 129 public function __construct(DatabaseAdapterInterface $adapter) { 130 $this->adapter = $adapter; 131 } 132 133 public function fetchById($id) { 134 $this->adapter->select("users", array("id" => $id)); 135 return $this->createUser($this->adapter->fetch()); 136 } 137 138 private function createUser($row) { 139 if (!$row) { 140 $factory = new \ProxyManager\Factory\NullObjectFactory(); 141 142 return $factory->createProxy('Entity\User'); 143 } 144 $user = new Entity\User($row["name"], $row["email"]); 145 $user->setId($row["id"]); 146 return $user; 147 } 148 } 149 </code> 150 </pre> 151 152 153 <hr /> 154 155 <h3 class="section-title">Proxying interfaces</h3> 156 157 <p>You can also generate proxies from an interface FQCN. By proxying an interface, you will only be able to access the methods defined by the interface itself, and like with the object, the methods are empty.</p> 158 159 <p>Tuning performance for production</p> 160 161 <p>See <a href="production.html">Tuning ProxyManager for Production.</a></p> 162 163 </main> 164 165 <footer class="site-footer" role="contentinfo"> 166 <div class="container"> 167 <div class="footer-logos"> 168 <ul> 169 <li><a href="index.html">Intro</a> | </li> 170 <li><a href="virtual-proxy.html">Virtual Proxy</a> | </li> 171 <li><a href="null-object.html">Null Objects</a> | </li> 172 <li><a href="ghost-object.html">Ghost Objects</a> | </li> 173 <li><a href="remote-object.html">Remote Object</a> | </li> 174 <li><a href="contributing.html">Contributing</a> | </li> 175 <li><a href="credits.html">Credits</a> | </li> 176 <li><a href="copyright.html">Copyright</a></li> 177 </ul> 178 </div> 179 </div> 180 181 <div class="bcms-clearfix"></div> 182 </footer> 183 <div class="bcms-clearfix"></div> 184 </body> 185 </html>
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