factories.rst

.. index::
   single: Dependency Injection; Factories

Using a Factory to Create Services

Symfony2's Service Container provides a powerful way of controlling the creation of objects, allowing you to specify arguments passed to the constructor as well as calling methods and setting parameters. Sometimes, however, this will not provide you with everything you need to construct your objects. For this situation, you can use a factory to create the object and tell the service container to call a method on the factory rather than directly instantiating the object.

Suppose you have a factory that configures and returns a new NewsletterManager object:

class NewsletterFactory
{
    public function get()
    {
        $newsletterManager = new NewsletterManager();

        // ...

        return $newsletterManager;
    }
}

To make the NewsletterManager object available as a service, you can configure the service container to use the NewsletterFactory factory class:

.. configuration-block::

    .. code-block:: yaml

        parameters:
            # ...
            newsletter_manager.class: NewsletterManager
            newsletter_factory.class: NewsletterFactory
        services:
            newsletter_manager:
                class:          "%newsletter_manager.class%"
                factory_class:  "%newsletter_factory.class%"
                factory_method: get

    .. code-block:: xml

        <parameters>
            <!-- ... -->
            <parameter key="newsletter_manager.class">NewsletterManager</parameter>
            <parameter key="newsletter_factory.class">NewsletterFactory</parameter>
        </parameters>

        <services>
            <service id="newsletter_manager"
                     class="%newsletter_manager.class%"
                     factory-class="%newsletter_factory.class%"
                     factory-method="get"
            />
        </services>

    .. code-block:: php

        use Symfony\Component\DependencyInjection\Definition;

        // ...
        $container->setParameter('newsletter_manager.class', 'NewsletterManager');
        $container->setParameter('newsletter_factory.class', 'NewsletterFactory');

        $container->setDefinition('newsletter_manager', new Definition(
            '%newsletter_manager.class%'
        ))->setFactoryClass(
            '%newsletter_factory.class%'
        )->setFactoryMethod(
            'get'
        );

When you specify the class to use for the factory (via factory_class) the method will be called statically. If the factory itself should be instantiated and the resulting object's method called (as in this example), configure the factory itself as a service:

.. configuration-block::

    .. code-block:: yaml

        parameters:
            # ...
            newsletter_manager.class: NewsletterManager
            newsletter_factory.class: NewsletterFactory
        services:
            newsletter_factory:
                class:            "%newsletter_factory.class%"
            newsletter_manager:
                class:            "%newsletter_manager.class%"
                factory_service:  newsletter_factory
                factory_method:   get

    .. code-block:: xml

        <parameters>
            <!-- ... -->
            <parameter key="newsletter_manager.class">NewsletterManager</parameter>
            <parameter key="newsletter_factory.class">NewsletterFactory</parameter>
        </parameters>

        <services>
            <service id="newsletter_factory" class="%newsletter_factory.class%"/>
            <service id="newsletter_manager"
                     class="%newsletter_manager.class%"
                     factory-service="newsletter_factory"
                     factory-method="get"
            />
        </services>

    .. code-block:: php

        use Symfony\Component\DependencyInjection\Definition;

        // ...
        $container->setParameter('newsletter_manager.class', 'NewsletterManager');
        $container->setParameter('newsletter_factory.class', 'NewsletterFactory');

        $container->setDefinition('newsletter_factory', new Definition(
            '%newsletter_factory.class%'
        ))
        $container->setDefinition('newsletter_manager', new Definition(
            '%newsletter_manager.class%'
        ))->setFactoryService(
            'newsletter_factory'
        )->setFactoryMethod(
            'get'
        );

Note

The factory service is specified by its id name and not a reference to the service itself. So, you do not need to use the @ syntax.

Passing Arguments to the Factory Method

If you need to pass arguments to the factory method, you can use the arguments options inside the service container. For example, suppose the get method in the previous example takes the templating service as an argument:

.. configuration-block::

    .. code-block:: yaml

        parameters:
            # ...
            newsletter_manager.class: NewsletterManager
            newsletter_factory.class: NewsletterFactory
        services:
            newsletter_factory:
                class:            "%newsletter_factory.class%"
            newsletter_manager:
                class:            "%newsletter_manager.class%"
                factory_service:  newsletter_factory
                factory_method:   get
                arguments:
                    - "@templating"

    .. code-block:: xml

        <parameters>
            <!-- ... -->
            <parameter key="newsletter_manager.class">NewsletterManager</parameter>
            <parameter key="newsletter_factory.class">NewsletterFactory</parameter>
        </parameters>

        <services>
            <service id="newsletter_factory" class="%newsletter_factory.class%"/>
            <service id="newsletter_manager"
                     class="%newsletter_manager.class%"
                     factory-service="newsletter_factory"
                     factory-method="get"
            >
                <argument type="service" id="templating" />
            </service>
        </services>

    .. code-block:: php

        use Symfony\Component\DependencyInjection\Definition;

        // ...
        $container->setParameter('newsletter_manager.class', 'NewsletterManager');
        $container->setParameter('newsletter_factory.class', 'NewsletterFactory');

        $container->setDefinition('newsletter_factory', new Definition(
            '%newsletter_factory.class%'
        ))
        $container->setDefinition('newsletter_manager', new Definition(
            '%newsletter_manager.class%',
            array(new Reference('templating'))
        ))->setFactoryService(
            'newsletter_factory'
        )->setFactoryMethod(
            'get'
        );