When overriding an existing definition, the original service is lost:
.. configuration-block::
.. code-block:: yaml
# config/services.yaml
services:
App\Mailer: ~
# this replaces the old App\Mailer definition with the new one, the
# old definition is lost
App\Mailer:
class: App\NewMailer
.. code-block:: xml
<!-- config/services.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
xmlns:xsd="http://www.w3.org/2001/XMLSchema-instance"
xsd:schemaLocation="http://symfony.com/schema/dic/services https://symfony.com/schema/dic/services/services-1.0.xsd">
<services>
<service id="App\Mailer"/>
<!-- this replaces the old App\Mailer definition with the new
one, the old definition is lost -->
<service id="App\Mailer" class="App\NewMailer"/>
</services>
</container>
.. code-block:: php
// config/services.php
namespace Symfony\Component\DependencyInjection\Loader\Configurator;
use App\Mailer;
use App\NewMailer;
return function(ContainerConfigurator $container) {
$services = $container->services();
$services->set(Mailer::class);
// this replaces the old App\Mailer definition with the new one, the
// old definition is lost
$services->set(Mailer::class, NewMailer::class);
};
Most of the time, that's exactly what you want to do. But sometimes,
you might want to decorate the old one instead (i.e. apply the Decorator pattern).
In this case, the old service should be kept around to be able to reference
it in the new one. This configuration replaces App\Mailer with a new one,
but keeps a reference of the old one as .inner:
.. configuration-block::
.. code-block:: yaml
# config/services.yaml
services:
App\Mailer: ~
App\DecoratingMailer:
# overrides the App\Mailer service
# but that service is still available as ".inner"
decorates: App\Mailer
.. code-block:: xml
<!-- config/services.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
xmlns:xsd="http://www.w3.org/2001/XMLSchema-instance"
xsd:schemaLocation="http://symfony.com/schema/dic/services https://symfony.com/schema/dic/services/services-1.0.xsd">
<services>
<service id="App\Mailer"/>
<!-- overrides the App\Mailer service
but that service is still available as ".inner" -->
<service id="App\DecoratingMailer"
decorates="App\Mailer"
/>
</services>
</container>
.. code-block:: php
// config/services.php
namespace Symfony\Component\DependencyInjection\Loader\Configurator;
use App\DecoratingMailer;
use App\Mailer;
return function(ContainerConfigurator $container) {
$services = $container->services();
$services->set(Mailer::class);
$services->set(DecoratingMailer::class)
// overrides the App\Mailer service
// but that service is still available as ".inner"
->decorate(Mailer::class);
};
The decorates option tells the container that the App\DecoratingMailer
service replaces the App\Mailer service. If you're using the
:ref:`default services.yaml configuration <service-container-services-load-example>`,
the decorated service is automatically injected when the constructor of the
decorating service has one argument type-hinted with the decorated service class.
If you are not using autowiring or the decorating service has more than one
constructor argument type-hinted with the decorated service class, you must
inject the decorated service explicitly (the ID of the decorated service is
automatically changed to '.inner'):
.. configuration-block::
.. code-block:: yaml
# config/services.yaml
services:
App\Mailer: ~
App\DecoratingMailer:
decorates: App\Mailer
# pass the old service as an argument
arguments: ['@.inner']
.. code-block:: xml
<!-- config/services.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
xmlns:xsd="http://www.w3.org/2001/XMLSchema-instance"
xsd:schemaLocation="http://symfony.com/schema/dic/services https://symfony.com/schema/dic/services/services-1.0.xsd">
<services>
<service id="App\Mailer"/>
<service id="App\DecoratingMailer"
decorates="App\Mailer"
>
<!-- pass the old service as an argument -->
<argument type="service" id=".inner"/>
</service>
</services>
</container>
.. code-block:: php
// config/services.php
namespace Symfony\Component\DependencyInjection\Loader\Configurator;
use App\DecoratingMailer;
use App\Mailer;
return function(ContainerConfigurator $container) {
$services = $container->services();
$services->set(Mailer::class);
$services->set(DecoratingMailer::class)
->decorate(Mailer::class)
// pass the old service as an argument
// In versions earlier to Symfony 5.1 the service() function was called ref()
->args([service('.inner')]);
};
.. versionadded:: 5.1
The special ``.inner`` value was introduced in Symfony 5.1. In previous
versions you needed to use: ``decorating_service_id + '.inner'``.
Tip
The visibility of the decorated App\Mailer service (which is an alias
for the new service) will still be the same as the original App\Mailer
visibility.
Note
The generated inner id is based on the id of the decorator service
(App\DecoratingMailer here), not of the decorated service (App\Mailer
here). You can control the inner service name via the decoration_inner_name
option:
.. configuration-block::
.. code-block:: yaml
# config/services.yaml
services:
App\DecoratingMailer:
# ...
decoration_inner_name: App\DecoratingMailer.wooz
arguments: ['@App\DecoratingMailer.wooz']
.. code-block:: xml
<!-- config/services.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
xmlns:xsd="http://www.w3.org/2001/XMLSchema-instance"
xsd:schemaLocation="http://symfony.com/schema/dic/services https://symfony.com/schema/dic/services/services-1.0.xsd">
<services>
<!-- ... -->
<service
id="App\DecoratingMailer"
decorates="App\Mailer"
decoration-inner-name="App\DecoratingMailer.wooz"
public="false"
>
<argument type="service" id="App\DecoratingMailer.wooz"/>
</service>
</services>
</container>
.. code-block:: php
// config/services.php
namespace Symfony\Component\DependencyInjection\Loader\Configurator;
use App\DecoratingMailer;
use App\Mailer;
return function(ContainerConfigurator $container) {
$services = $container->services();
$services->set(Mailer::class);
$services->set(DecoratingMailer::class)
->decorate(Mailer::class, DecoratingMailer::class.'.wooz')
->args([service(DecoratingMailer::class.'.wooz')]);
};
When applying multiple decorators to a service, you can control their order with
the decoration_priority option. Its value is an integer that defaults to
0 and higher priorities mean that decorators will be applied earlier.
.. configuration-block::
.. code-block:: yaml
# config/services.yaml
services:
Foo: ~
Bar:
decorates: Foo
decoration_priority: 5
arguments: ['@.inner']
Baz:
decorates: Foo
decoration_priority: 1
arguments: ['@.inner']
.. code-block:: xml
<!-- config/services.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 https://symfony.com/schema/dic/services/services-1.0.xsd">
<services>
<service id="Foo"/>
<service id="Bar" decorates="Foo" decoration-priority="5">
<argument type="service" id=".inner"/>
</service>
<service id="Baz" decorates="Foo" decoration-priority="1">
<argument type="service" id=".inner"/>
</service>
</services>
</container>
.. code-block:: php
// config/services.php
namespace Symfony\Component\DependencyInjection\Loader\Configurator;
return function(ContainerConfigurator $container) {
$services = $container->services();
$services->set(\Foo::class);
$services->set(\Bar::class)
->decorate(\Foo::class, null, 5)
->args([service('.inner')]);
$services->set(\Baz::class)
->decorate(\Foo::class, null, 1)
->args([service('.inner')]);
};
The generated code will be the following:
$this->services[Foo::class] = new Baz(new Bar(new Foo()));
An alternative to using decoration priorities is to create a stack of
ordered services, each one decorating the next:
.. configuration-block::
.. code-block:: yaml
# config/services.yaml
services:
decorated_foo_stack:
stack:
- class: Baz
arguments: ['@.inner']
- class: Bar
arguments: ['@.inner']
- class: Foo
# using the short syntax:
decorated_foo_stack:
stack:
- Baz: ['@.inner']
- Bar: ['@.inner']
- Foo: ~
# can be simplified when autowiring is enabled:
decorated_foo_stack:
stack:
- Baz: ~
- Bar: ~
- Foo: ~
.. code-block:: xml
<!-- config/services.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
https://symfony.com/schema/dic/services/services-1.0.xsd"
>
<services>
<stack id="decorated_foo_stack">
<service class="Baz">
<argument type="service" id=".inner"/>
</service>
<service class="Bar">
<argument type="service" id=".inner"/>
</service>
<service class="Foo"/>
</stack>
<!-- can be simplified when autowiring is enabled: -->
<stack id="decorated_foo_stack">
<service class="Baz"/>
<service class="Bar"/>
<service class="Foo"/>
</stack>
</services>
</container>
.. code-block:: php
// config/services.php
namespace Symfony\Component\DependencyInjection\Loader\Configurator;
return function(ContainerConfigurator $container) {
$container->services()
->stack('decorated_foo_stack', [
inline_service(\Baz::class)->args([service('.inner')]),
inline_service(\Bar::class)->args([service('.inner')]),
inline_service(\Foo::class),
])
// can be simplified when autowiring is enabled:
->stack('decorated_foo_stack', [
inline_service(\Baz::class),
inline_service(\Bar::class),
inline_service(\Foo::class),
])
;
};
The result will be the same as in the previous section:
$this->services['decorated_foo_stack'] = new Baz(new Bar(new Foo()));
Like aliases, a stack can only use public and deprecated attributes.
Each frame of the stack can be either an inlined service, a reference or a
child definition.
The latter allows embedding stack definitions into each others, here's an
advanced example of composition:
.. configuration-block::
.. code-block:: yaml
# config/services.yaml
services:
some_decorator:
class: App\Decorator
embedded_stack:
stack:
- alias: some_decorator
- App\Decorated: ~
decorated_foo_stack:
stack:
- parent: embedded_stack
- Baz: ~
- Bar: ~
- Foo: ~
.. code-block:: xml
<!-- config/services.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
https://symfony.com/schema/dic/services/services-1.0.xsd"
>
<services>
<service id="some_decorator" class="App\Decorator"/>
<stack id="embedded_stack">
<service alias="some_decorator"/>
<service class="App\Decorated"/>
</stack>
<stack id="decorated_foo_stack">
<service parent="embedded_stack"/>
<service class="Baz"/>
<service class="Bar"/>
<service class="Foo"/>
</stack>
</services>
</container>
.. code-block:: php
// config/services.php
namespace Symfony\Component\DependencyInjection\Loader\Configurator;
use App\Decorated;
use App\Decorator;
return function(ContainerConfigurator $container) {
$container->services()
->set('some_decorator', Decorator::class)
->stack('embedded_stack', [
service('some_decorator'),
inline_service(Decorated::class),
])
->stack('decorated_foo_stack', [
inline_service()->parent('embedded_stack'),
inline_service(\Baz::class),
inline_service(\Bar::class),
inline_service(\Foo::class),
])
;
};
The result will be:
$this->services['decorated_foo_stack'] = new App\Decorator(new App\Decorated(new Baz(new Bar(new Foo()))));
Note
To change existing stacks (i.e. from a compiler pass), you can access each
frame by its generated id with the following structure:
.stack_id.frame_key.
From the example above, .decorated_foo_stack.1 would be a reference to
the inlined Baz service and .decorated_foo_stack.0 to the embedded
stack.
To get more explicit ids, you can give a name to each frame:
.. configuration-block::
.. code-block:: yaml
# ...
decorated_foo_stack:
stack:
first:
parent: embedded_stack
second:
Baz: ~
# ...
.. code-block:: xml
<!-- ... -->
<stack id="decorated_foo_stack">
<service id="first" parent="embedded_stack"/>
<service id="second" class="Baz"/>
<!-- ... -->
</stack>
.. code-block:: php
// ...
->stack('decorated_foo_stack', [
'first' => inline_service()->parent('embedded_stack'),
'second' => inline_service(\Baz::class),
// ...
])
The Baz frame id will now be .decorated_foo_stack.second.
.. versionadded:: 5.1
The ability to define ``stack`` was introduced in Symfony 5.1.
When you decorate a service that doesn't exist, the decoration_on_invalid
option allows you to choose the behavior to adopt.
Three different behaviors are available:
exception: AServiceNotFoundExceptionwill be thrown telling that decorator's dependency is missing. (default)ignore: The container will remove the decorator.null: The container will keep the decorator service and will set the decorated one tonull.
.. configuration-block::
.. code-block:: yaml
# config/services.yaml
Foo: ~
Bar:
decorates: Foo
decoration_on_invalid: ignore
arguments: ['@.inner']
.. code-block:: xml
<!-- config/services.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 https://symfony.com/schema/dic/services/services-1.0.xsd">
<services>
<service id="Foo"/>
<service id="Bar" decorates="Foo" decoration-on-invalid="ignore">
<argument type="service" id=".inner"/>
</service>
</services>
</container>
.. code-block:: php
// config/services.php
namespace Symfony\Component\DependencyInjection\Loader\Configurator;
use Symfony\Component\DependencyInjection\ContainerInterface;
return function(ContainerConfigurator $container) {
$services = $container->services();
$services->set(Foo::class);
$services->set(Bar::class)
->decorate(Foo::class, null, 0, ContainerInterface::IGNORE_ON_INVALID_REFERENCE)
->args([service('.inner')])
;
};
Caution!
When using null, you may have to update the decorator constructor in
order to make decorated dependency nullable:
// src/Service/DecoratorService.php
namespace App\Service;
use Acme\OptionalBundle\Service\OptionalService;
class DecoratorService
{
private $decorated;
public function __construct(?OptionalService $decorated)
{
$this->decorated = $decorated;
}
public function tellInterestingStuff(): string
{
if (!$this->decorated) {
return 'Just one interesting thing';
}
return $this->decorated->tellInterestingStuff().' + one more interesting thing';
}
}
Note
Sometimes, you may want to add a compiler pass that creates service
definitions on the fly. If you want to decorate such a service,
be sure that your compiler pass is registered with PassConfig::TYPE_BEFORE_OPTIMIZATION
type so that the decoration pass will be able to find the created services.