How to Decorate Services
How to Decorate Services¶
When overriding an existing definition (e.g. when applying the Decorator pattern), the original service is lost:
- YAML
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services: app.mailer: class: AppBundle\Mailer # this replaces the old app.mailer definition with the new one, the # old definition is lost app.mailer: class: AppBundle\DecoratingMailer
- XML
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<?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" class="AppBundle\Mailer" /> <!-- this replaces the old app.mailer definition with the new one, the old definition is lost --> <service id="app.mailer" class="AppBundle\DecoratingMailer" /> </services> </container>
- PHP
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use AppBundle\Mailer; use AppBundle\DecoratingMailer; $container->register('app.mailer', Mailer::class); // this replaces the old app.mailer definition with the new one, the // old definition is lost $container->register('app.mailer', 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:
- YAML
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services: app.mailer: class: AppBundle\Mailer app.decorating_mailer: class: AppBundle\DecoratingMailer # overrides the app.mailer service # but that service is still available as app.decorating_mailer.inner decorates: app.mailer # pass the old service as an argument arguments: ['@app.decorating_mailer.inner'] # private, because usually you do not need to fetch app.decorating_mailer directly public: false
- XML
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<?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" class="AppBundle\Mailer" /> <service id="app.decorating_mailer" class="AppBundle\DecoratingMailer" decorates="app.mailer" public="false" > <argument type="service" id="app.decorating_mailer.inner" /> </service> </services> </container>
- PHP
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use AppBundle\DecoratingMailer; use AppBundle\Mailer; use Symfony\Component\DependencyInjection\Reference; $container->register('app.mailer', Mailer::class); $container->register('app.decorating_mailer', DecoratingMailer::class) ->setDecoratedService('app.mailer') ->addArgument(new Reference('app.decorating_mailer.inner')) ->setPublic(false) ;
The decorates
option tells the container that the app.decorating_mailer
service
replaces the app.mailer
service. The old app.mailer
service is renamed to
app.decorating_mailer.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.decorating_mailer
here), not of the decorated service (app.mailer
here). You can control the inner service name via the decoration_inner_name
option:
- YAML
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services: app.decorating_mailer: # ... decoration_inner_name: app.decorating_mailer.wooz arguments: ['@app.decorating_mailer.wooz']
- XML
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<?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.decorating_mailer" class="AppBundle\DecoratingMailer" decorates="app.mailer" decoration-inner-name="app.decorating_mailer.wooz" public="false" > <argument type="service" id="app.decorating_mailer.wooz" /> </service> </services> </container>
- PHP
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use AppBundle\DecoratingMailer; use Symfony\Component\DependencyInjection\Reference; $container->register('app.decorating_mailer', DecoratingMailer::class) ->setDecoratedService('app.mailer', 'app.decorating_mailer.wooz') ->addArgument(new Reference('app.decorating_mailer.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.
- YAML
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foo: class: Foo bar: class: Bar public: false decorates: foo decoration_priority: 5 arguments: ['@bar.inner'] baz: class: Baz public: false decorates: foo decoration_priority: 1 arguments: ['@baz.inner']
- XML
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<?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="Foo" /> <service id="bar" class="Bar" decorates="foo" decoration-priority="5" public="false"> <argument type="service" id="bar.inner" /> </service> <service id="baz" class="Baz" decorates="foo" decoration-priority="1" public="false"> <argument type="service" id="baz.inner" /> </service> </services> </container>
- PHP
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use Symfony\Component\DependencyInjection\Reference; $container->register('foo', 'Foo') $container->register('bar', 'Bar') ->addArgument(new Reference('bar.inner')) ->setPublic(false) ->setDecoratedService('foo', null, 5); $container->register('baz', 'Baz') ->addArgument(new Reference('baz.inner')) ->setPublic(false) ->setDecoratedService('foo', null, 1);
The generated code will be the following:
$this->services['foo'] = new Baz(new Bar(new Foo()));
This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.