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. This means that you can fetch it from the container using the get() method:

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

In some cases, a service only exists to be injected into another service and is not intended to be fetched directly from the container as shown above.

In these cases, to get a minor performance boost, you can set the service to be not public (i.e. private):

YAML

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

XML

<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd">

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

PHP

use Symfony\Component\DependencyInjection\Definition;

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

What makes private services special is that, if they are only injected once, they are converted from services to inlined instantiations (e.g. new PrivateThing()). This increases the container’s performance.

Now that the service is private, you should not fetch the service directly from the container:

$container->get('foo');

This may or may not work, depending on if the service could be inlined. Simply said: A service can be marked as private if you do not want to access it directly from your code.

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

注解

Services are by default public.

Synthetic Services¶

Synthetic services are services that are injected into the container instead of being created by the container.

For example, if you’re using the HttpKernel component with the DependencyInjection component, then the request service is injected in the ContainerAwareHttpKernel::handle() method when entering the request scope. The class does not exist when there is no request, so it can’t be included in the container configuration. Also, the service should be different for every subrequest in the application.

To create a synthetic service, set synthetic to true:

YAML

services:
    request:
        synthetic: true

XML

<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd">

    <services>
        <service id="request" synthetic="true" />
    </services>
</container>

PHP

use Symfony\Component\DependencyInjection\Definition;

$container
    ->setDefinition('request', new Definition())
    ->setSynthetic(true);

As you see, only the synthetic option is set. All other options are only used to configure how a service is created by the container. As the service isn’t created by the container, these options are omitted.

Now, you can inject the class by using Container::set:

// ...
$container->set('request', new MyRequest(...));

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.

YAML

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

XML

<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd">

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

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

PHP

use Symfony\Component\DependencyInjection\Definition;

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

$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

小技巧

In YAML, you can also use a shortcut to alias a service:

services:
   foo:
     class: Example\Foo
   bar: "@foo"

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.

YAML

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

XML

<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd">

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

PHP

use Symfony\Component\DependencyInjection\Definition;

$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 statement require_once, which means that your file will be included only once per request.