How to Decorate Services
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How to Decorate Services
When overriding an existing definition, the original service is lost:
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# 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
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<!-- 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 http://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>
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// config/services.php
use App\Mailer;
use App\NewMailer;
$container->register(Mailer::class);
// this replaces the old App\Mailer definition with the new one, the
// old definition is lost
$container->register(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 App\DecoratingMailer.inner
:
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# config/services.yaml
services:
App\Mailer: ~
App\DecoratingMailer:
# overrides the App\Mailer service
# but that service is still available as App\DecoratingMailer.inner
decorates: App\Mailer
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<!-- 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 http://symfony.com/schema/dic/services/services-1.0.xsd">
<services>
<service id="App\Mailer" />
<service id="App\DecoratingMailer"
decorates="App\Mailer"
/>
</services>
</container>
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// config/services.php
use App\DecoratingMailer;
use App\Mailer;
use Symfony\Component\DependencyInjection\Reference;
$container->register(Mailer::class);
$container->register(DecoratingMailer::class)
->setDecoratedService(Mailer::class)
;
The decorates
option tells the container that the App\DecoratingMailer
service replaces the App\Mailer
service. If you're using the
default services.yaml configuration,
the decorated service is automatically injected when the constructor of the
decorating service has one argument type-hinted with the decorated service class.
4.1
The autowiring of the decorated service was introduced in Symfony 4.1.
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 decorating_service_id + '.inner'
):
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# config/services.yaml
services:
App\Mailer: ~
App\DecoratingMailer:
decorates: App\Mailer
# pass the old service as an argument
arguments: ['@App\DecoratingMailer.inner']
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<!-- 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 http://symfony.com/schema/dic/services/services-1.0.xsd">
<services>
<service id="App\Mailer" />
<service id="App\DecoratingMailer"
decorates="App\Mailer"
>
<argument type="service" id="App\DecoratingMailer.inner" />
</service>
</services>
</container>
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// config/services.php
use App\DecoratingMailer;
use App\Mailer;
use Symfony\Component\DependencyInjection\Reference;
$container->register(Mailer::class);
$container->register(DecoratingMailer::class)
->setDecoratedService(Mailer::class)
->addArgument(new Reference(DecoratingMailer::class.'.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:
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# config/services.yaml
services:
App\DecoratingMailer:
# ...
decoration_inner_name: App\DecoratingMailer.wooz
arguments: ['@App\DecoratingMailer.wooz']
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<!-- 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 http://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>
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// config/services.php
use App\DecoratingMailer;
use Symfony\Component\DependencyInjection\Reference;
$container->register(DecoratingMailer::class)
->setDecoratedService(App\Mailer, DecoratingMailer::class.'.wooz')
->addArgument(new Reference(DecoratingMailer::class.'.wooz'))
// ...
;
Decoration Priority
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.
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# config/services.yaml
Foo: ~
Bar:
public: false
decorates: Foo
decoration_priority: 5
arguments: ['@Bar.inner']
Baz:
public: false
decorates: Foo
decoration_priority: 1
arguments: ['@Baz.inner']
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<!-- 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 http://symfony.com/schema/dic/services/services-1.0.xsd">
<services>
<service id="Foo" />
<service id="Bar" decorates="Foo" decoration-priority="5" public="false">
<argument type="service" id="Bar.inner" />
</service>
<service id="Baz" decorates="Foo" decoration-priority="1" public="false">
<argument type="service" id="Baz.inner" />
</service>
</services>
</container>
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// config/services.php
use Symfony\Component\DependencyInjection\Reference;
$container->register(Foo::class)
$container->register(Bar::class)
->addArgument(new Reference(Bar::class.'.inner'))
->setPublic(false)
->setDecoratedService(Foo::class, null, 5);
$container->register(Baz::class)
->addArgument(new Reference(Baz::class.'.inner'))
->setPublic(false)
->setDecoratedService(Foo::class, null, 1);
The generated code will be the following:
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$this->services[Foo::class] = new Baz(new Bar(new Foo()));