diff --git a/en/cookbook/decorator-pattern.rst b/en/cookbook/decorator-pattern.rst new file mode 100644 index 000000000..38bf3ef54 --- /dev/null +++ b/en/cookbook/decorator-pattern.rst @@ -0,0 +1,273 @@ +Persisting the Decorator Pattern +================================ + +.. sectionauthor:: Chris Woodford + +This recipe will show you a simple example of how you can use +Doctrine 2 to persist an implementaton of the +`Decorator Pattern `_ + +Component +--------- + +The ``Component`` class needs to be persisted, so it's going to +be an ``Entity``. As the top of the inheritance hierarchy, it's going +to have to define the persistent inheritance. For this example, we +will use Single Table Inheritance, but Class Table Inheritance +would work as well. In the discriminator map, we will define two +concrete subclasses, ``ConcreteComponent`` and ``ConcreteDecorator``. + +.. code-block:: php + + id; + } + + /** + * Set name + * @param string $name + */ + public function setName($name) + { + $this->name = $name; + } + + /** + * Get name + * @return string $name + */ + public function getName() + { + return $this->name; + } + + } + +ConcreteComponent +----------------- + +The ``ConcreteComponent`` class is pretty simple and doesn't do much +more than extend the abstract ``Component`` class (only for the +purpose of keeping this example simple). + +.. code-block:: php + + setDecorates($c); + } + + /** + * (non-PHPdoc) + * @see Test.Component::getName() + */ + public function getName() + { + return 'Decorated ' . $this->getDecorates()->getName(); + } + + /** + * the component being decorated + * @return Component + */ + protected function getDecorates() + { + return $this->decorates; + } + + /** + * sets the component being decorated + * @param Component $c + */ + protected function setDecorates(Component $c) + { + $this->decorates = $c; + } + + } + +All operations on the ``Decorator`` (i.e. persist, remove, etc) will +cascade from the ``Decorator`` to the ``Component``. This means that +when we persist a ``Decorator``, Doctrine will take care of +persisting the chain of decorated objects for us. A ``Decorator`` can +be treated exactly as a ``Component`` when it comes time to +persisting it. + +The ``Decorator's`` constructor accepts an instance of a +``Component``, as defined by the ``Decorator`` pattern. The +setDecorates/getDecorates methods have been defined as protected to +hide the fact that a ``Decorator`` is decorating a ``Component`` and +keeps the ``Component`` interface and the ``Decorator`` interface +identical. + +To illustrate the intended result of the ``Decorator`` pattern, the +getName() method has been overridden to append a string to the +``Component's`` getName() method. + +ConcreteDecorator +----------------- + +The final class required to complete a simple implementation of the +Decorator pattern is the ``ConcreteDecorator``. In order to further +illustrate how the ``Decorator`` can alter data as it moves through +the chain of decoration, a new field, "special", has been added to +this class. The getName() has been overridden and appends the value +of the getSpecial() method to its return value. + +.. code-block:: php + + special = $special; + } + + /** + * Get special + * @return string $special + */ + public function getSpecial() + { + return $this->special; + } + + /** + * (non-PHPdoc) + * @see Test.Component::getName() + */ + public function getName() + { + return '[' . $this->getSpecial() + . '] ' . parent::getName(); + } + + } + +Examples +-------- + +Here is an example of how to persist and retrieve your decorated +objects + +.. code-block:: php + + setName('Test Component 1'); + $em->persist($c); // assigned unique ID = 1 + + // create a new concrete decorator + $c = new ConcreteComponent(); + $c->setName('Test Component 2'); + + $d = new ConcreteDecorator($c); + $d->setSpecial('Really'); + $em->persist($d); + // assigns c as unique ID = 2, and d as unique ID = 3 + + $em->flush(); + + $c = $em->find('Test\Component', 1); + $d = $em->find('Test\Component', 3); + + echo get_class($c); + // prints: Test\Component\ConcreteComponent + + echo $c->getName(); + // prints: Test Component 1 + + echo get_class($d) + // prints: Test\Component\ConcreteDecorator + + echo $d->getName(); + // prints: [Really] Decorated Test Component 2 + diff --git a/en/index.rst b/en/index.rst index a577e01e9..ef2638705 100644 --- a/en/index.rst +++ b/en/index.rst @@ -55,6 +55,7 @@ Cookbook :maxdepth: 1 cookbook/aggregate-fields + cookbook/decorator-pattern cookbook/dql-custom-walkers cookbook/dql-user-defined-functions cookbook/implementing-arrayaccess-for-domain-objects