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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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\DecoratingMailerMost of the time, that's exactly what you want to do. But sometimes,
you might want to decorate the old one instead. 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.decorating_mailer.inner:
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services:
# ...
app.decorating_mailer:
class: AppBundle\DecoratingMailer
decorates: app.mailer
arguments: ['@app.decorating_mailer.inner']
public: falseHere is what's going on here: the decorates option tells the container that
the app.decorating_mailer service replaces the app.mailer service. By
convention, the old app.mailer service is renamed to
app.decorating_mailer.inner, so you can inject it into your new service.
Tip
Most of the time, the decorator should be declared private, as you will not
need to retrieve it as app.decorating_mailer from the container.
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.decorating_mailer here), not of the decorated service (app.mailer
here). This is mandatory to allow several decorators on the same service
(they need to have different generated inner ids).
You can change the inner service name if you want to using the
decoration_inner_name option:
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services:
app.mailer:
# ...
decoration_inner_name: app.decorating_mailer.wooz
arguments: ['@app.decorating_mailer.wooz']Decoration Priority
If you want to apply more than one decorator to a service, you can control their order by configuring the priority of decoration, this can be any integer number (decorators with higher priorities will be applied first).
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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']The generated code will be the following:
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$this->services['foo'] = new Baz(new Bar(new Foo())));
