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null-object.html
001 <!DOCTYPE html>
002 <html class="no-js" id="top">
003 <head>
004 <title>ProxyManager - Null object</title>
005
006 <meta name="description" content="A proxyManager write in php" />
007 <meta name="keywords" content="ProxyManager, proxy, manager, ocramius, Marco Pivetta, php, null object" />
008 <meta name="viewport" content="width=device-width, initial-scale=1, minimum-scale=1" />
009 <link href='http://fonts.googleapis.com/css?family=Source+Sans+Pro:200,300,400,600' rel='stylesheet' type='text/css'>
010 <link href="css/styles.css" rel="stylesheet" />
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012 <script src="//cdnjs.cloudflare.com/ajax/libs/highlight.js/8.3/highlight.min.js"></script>
013 <script>hljs.initHighlightingOnLoad();</script>
014 <link rel="shortcut icon" href="favicon.ico">
015 </head>
016 <body>
017
018 <header class="site-header">
019 <div class="container">
020 <h1><a href="index.html"><img alt="ProxyManager" src="img/block.png" /></a></h1>
021
022 <nav class="main-nav" role="navigation">
023 <ul>
024 <li><a href="https://github.com/Ocramius/ProxyManager" target="_blank">Github</a>
025 <div class="bcms-clearfix"></div>
026 </li>
027 </ul>
028 </nav>
029 </div>
030 </header>
031 <main role="main">
032 <section class="component-content">
033
034 <div class="component-demo" id="live-demo">
035 <div class="container">
036 <div class="main-wrapper" style="text-align: right">
037 <iframe src="http://ghbtns.com/github-btn.html?user=ocramius&repo=ProxyManager&type=fork&count=true&size=large"
038 allowtransparency="true" frameborder="0" scrolling="0" width="310" height="40"></iframe>
039
040 <iframe src="http://ghbtns.com/github-btn.html?user=ocramius&repo=ProxyManager&type=watch&count=true&size=large"
041 allowtransparency="true" frameborder="0" scrolling="0" width="200" height="40"></iframe>
042
043 </div>
044 <div class="bcms-clearfix bcms-clearfix"></div>
045 </div>
046 </div>
047 <div class="component-info">
048 <div class="container">
049 <aside class="sidebar">
050 <nav class="spy-nav">
051 <ul>
052 <li><a href="index.html">Intro</a></li>
053 <li><a href="virtual-proxy.html">Virtual Proxy</a></li>
054 <li><a href="null-object.html">Null Objects</a></li>
055 <li><a href="ghost-object.html">Ghost Objects</a></li>
056 <li><a href="remote-object.html">Remote Object</a></li>
057 <li><a href="contributing.html">Contributing</a></li>
058 <li><a href="credits.html">Credits</a></li>
059 <li><a href="copyright.html">Copyright</a></li>
060 </ul>
061 </nav>
062 <div class="bcms-clearfix bcms-clearfix"></div>
063 <a class="btn btn-action btn-full download-component"
064 href="download.html">Download</a>
065 <div class="bcms-clearfix"></div>
066 </aside>
067
068 <div class="content">
069 <div class="bcms-clearfix"></div>
070 <h3 class="section-title">Null Object Proxy</h3>
071 <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>
072 <hr />
073
074 <h3 class="section-title">What is null object proxy ?</h3>
075
076 <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>
077
078 <hr />
079
080 <h3 class="section-title">Usage examples</h3>
081
082 <pre>
083 <code class="php">
084 class UserMapper
085 {
086 private $adapter;
087
088 public function __construct(DatabaseAdapterInterface $adapter) {
089 $this->adapter = $adapter;
090 }
091
092 public function fetchById($id) {
093 $this->adapter->select("users", array("id" => $id));
094 if (!$row = $this->adapter->fetch()) {
095 return null;
096 }
097 return $this->createUser($row);
098 }
099
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>
186