How to Decorate Services
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How to Decorate Services
When overriding an existing definition (e.g. when applying the Decorator pattern), 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\DecoratingMailer
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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\DecoratingMailer" />
</services>
</container>
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// config/services.php
use App\Mailer;
use App\DecoratingMailer;
$container->register(Mailer::class);
// this replaces the old App\Mailer definition with the new one, the
// old definition is lost
$container->register(Mailer::class, DecoratingMailer::class);
Most of the time, that's exactly what you want to do. But sometimes, you might want to decorate the old service instead and keep the old service so that you can reference it:
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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
# pass the old service as an argument
arguments: ['@App\DecoratingMailer.inner']
# private, because usually you do not need to fetch App\DecoratingMailer directly
public: false
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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"
public="false"
>
<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'))
->setPublic(false)
;
The decorates
option tells the container that the App\DecoratingMailer
service
replaces the App\Mailer
service. The old App\Mailer
service is renamed to
App\DecoratingMailer.inner
so you can inject it into your new service.
Tip
The visibility (public) 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()));