.. index::
   single: Dependency Injection; Advanced configuration

Advanced Container Configuration
================================

Marking Services as public / private
------------------------------------

When defining services, you'll usually want to be able to access these definitions
within your application code. These services are called ``public``. For example,
the ``doctrine`` service registered with the container when using the DoctrineBundle
is a public service as you can access it via::

   $doctrine = $container->get('doctrine');

However, there are use-cases when you don't want a service to be public. This
is common when a service is only defined because it could be used as an
argument for another service.

.. note::

    If you use a private service as an argument to only one other service,
    this will result in an inlined instantiation (e.g. ``new PrivateFooBar()``)
    inside this other service, making it publicly unavailable at runtime.

Simply said: A service will be private when you do not want to access it
directly from your code.

Here is an example:

.. configuration-block::

    .. code-block:: yaml

        services:
           foo:
             class: Example\Foo
             public: false

    .. code-block:: xml

        <service id="foo" class="Example\Foo" public="false" />

    .. code-block:: php

        $definition = new Definition('Example\Foo');
        $definition->setPublic(false);
        $container->setDefinition('foo', $definition);

Now that the service is private, you *cannot* call::

    $container->get('foo');

However, if a service has been marked as private, you can still alias it (see
below) to access this service (via the alias).

.. note::

   Services are by default public.

Aliasing
--------

You may sometimes want to use shortcuts to access some services. You can
do so by aliasing them and, furthermore, you can even alias non-public
services.

.. configuration-block::

    .. code-block:: yaml

        services:
           foo:
             class: Example\Foo
           bar:
             alias: foo

    .. code-block:: xml

        <service id="foo" class="Example\Foo"/>

        <service id="bar" alias="foo" />

    .. code-block:: php

        $definition = new Definition('Example\Foo');
        $container->setDefinition('foo', $definition);

        $containerBuilder->setAlias('bar', 'foo');

This means that when using the container directly, you can access the ``foo``
service by asking for the ``bar`` service like this::

    $container->get('bar'); // Would return the foo service

Requiring files
---------------

There might be use cases when you need to include another file just before
the service itself gets loaded. To do so, you can use the ``file`` directive.

.. configuration-block::

    .. code-block:: yaml

        services:
           foo:
             class: Example\Foo\Bar
             file: "%kernel.root_dir%/src/path/to/file/foo.php"

    .. code-block:: xml

        <service id="foo" class="Example\Foo\Bar">
            <file>%kernel.root_dir%/src/path/to/file/foo.php</file>
        </service>

    .. code-block:: php

        $definition = new Definition('Example\Foo\Bar');
        $definition->setFile('%kernel.root_dir%/src/path/to/file/foo.php');
        $container->setDefinition('foo', $definition);

Notice that Symfony will internally call the PHP function require_once
which means that your file will be included only once per request.