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msd2/phpBB3/vendor/ocramius/proxy-manager/docs/null-object.md

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+# Null Object Proxy
+
+A Null Object proxy is a [null object pattern](http://en.wikipedia.org/wiki/Null_Object_pattern) implementation.
+The proxy factory creates a new object with defined neutral behavior based on an other object, class name or interface.
+
+## What is null object proxy ?
+
+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.
+
+## Usage examples
+
+```php
+class UserMapper
+{   
+    private $adapter;
+    
+    public function __construct(DatabaseAdapterInterface $adapter) {
+        $this->adapter = $adapter;
+    }
+
+    public function fetchById($id) {
+        $this->adapter->select("users", array("id" => $id));
+        if (!$row = $this->adapter->fetch()) {
+            return null;
+        }
+        return $this->createUser($row);
+    }
+     
+    private function createUser(array $row) {
+        $user = new Entity\User($row["name"], $row["email"]);
+        $user->setId($row["id"]);
+        return $user;
+    }
+}
+```
+
+If you want to remove conditionals from client code, you need to have a version of the entity conforming to the corresponding 
+interface. With the Null Object Proxy, you can build this object :
+
+```php
+$factory = new \ProxyManager\Factory\NullObjectFactory();
+
+$nullUser = $factory->createProxy('Entity\User');
+
+var_dump($nullUser->getName()); // empty return
+```
+
+You can now return a valid entity :
+
+```php
+class UserMapper
+{   
+    private $adapter;
+    
+    public function __construct(DatabaseAdapterInterface $adapter) {
+        $this->adapter = $adapter;
+    }
+
+    public function fetchById($id) {
+        $this->adapter->select("users", array("id" => $id));
+        return $this->createUser($this->adapter->fetch());
+    }
+     
+    private function createUser($row) {
+        if (!$row) {
+            $factory = new \ProxyManager\Factory\NullObjectFactory();
+
+            return $factory->createProxy('Entity\User');
+        }
+        $user = new Entity\User($row["name"], $row["email"]);
+        $user->setId($row["id"]);
+        return $user; 
+    }
+}
+```
+
+## Proxying interfaces
+
+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.
+
+## Tuning performance for production
+
+See [Tuning ProxyManager for Production](https://github.com/Ocramius/ProxyManager/blob/master/docs/tuning-for-production.md).