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   1  # Null Object Proxy
   2  
   3  A Null Object proxy is a [null object pattern](http://en.wikipedia.org/wiki/Null_Object_pattern) implementation.
   4  The proxy factory creates a new object with defined neutral behavior based on an other object, class name or interface.
   5  
   6  ## What is null object proxy ?
   7  
   8  In your application, when you can't return the object related to the request, the consumer of the model must check 
   9  for the return value and handle the failing condition gracefully, thus generating an explosion of conditionals throughout your code.
  10  Fortunately, this seemingly-tangled situation can be sorted out simply by creating a polymorphic implementation of the 
  11  domain object, which would implement the same interface as the one of the object in question, only that its methods 
  12  wouldn’t do anything, therefore offloading client code from doing repetitive checks for ugly null values when the operation
  13   is executed.
  14  
  15  ## Usage examples
  16  
  17  ```php
  18  class UserMapper
  19  {   
  20      private $adapter;
  21      
  22      public function __construct(DatabaseAdapterInterface $adapter) {
  23          $this->adapter = $adapter;
  24      }
  25  
  26      public function fetchById($id) {
  27          $this->adapter->select("users", array("id" => $id));
  28          if (!$row = $this->adapter->fetch()) {
  29              return null;
  30          }
  31          return $this->createUser($row);
  32      }
  33       
  34      private function createUser(array $row) {
  35          $user = new Entity\User($row["name"], $row["email"]);
  36          $user->setId($row["id"]);
  37          return $user;
  38      }
  39  }
  40  ```
  41  
  42  If you want to remove conditionals from client code, you need to have a version of the entity conforming to the corresponding 
  43  interface. With the Null Object Proxy, you can build this object :
  44  
  45  ```php
  46  $factory = new \ProxyManager\Factory\NullObjectFactory();
  47  
  48  $nullUser = $factory->createProxy('Entity\User');
  49  
  50  var_dump($nullUser->getName()); // empty return
  51  ```
  52  
  53  You can now return a valid entity :
  54  
  55  ```php
  56  class UserMapper
  57  {   
  58      private $adapter;
  59      
  60      public function __construct(DatabaseAdapterInterface $adapter) {
  61          $this->adapter = $adapter;
  62      }
  63  
  64      public function fetchById($id) {
  65          $this->adapter->select("users", array("id" => $id));
  66          return $this->createUser($this->adapter->fetch());
  67      }
  68       
  69      private function createUser($row) {
  70          if (!$row) {
  71              $factory = new \ProxyManager\Factory\NullObjectFactory();
  72  
  73              return $factory->createProxy('Entity\User');
  74          }
  75          $user = new Entity\User($row["name"], $row["email"]);
  76          $user->setId($row["id"]);
  77          return $user; 
  78      }
  79  }
  80  ```
  81  
  82  ## Proxying interfaces
  83  
  84  You can also generate proxies from an interface FQCN. By proxying an interface, you will only be able to access the
  85  methods defined by the interface itself, and like with the object, the methods are empty.
  86  
  87  ## Tuning performance for production
  88  
  89  See [Tuning ProxyManager for Production](https://github.com/Ocramius/ProxyManager/blob/master/docs/tuning-for-production.md).