How to Decorate Services

Replace a service with a new implementation while preserving access to the original.

This configuration replaces app.mailer with a new one, but keeps a reference of the old one as app.decorating_mailer.inner:

YAML

services:
    app.mailer:
        class: ./AppBundle/Mailer

    app.decorating_mailer:
      class: ./AppBundle/DecoratingMailer
      decorates: app.mailer
      arguments: ['@app.decorating_mailer.inner']
      public: false

JS

import DecoratingMailer from './DecoratingMailer'
import {Reference} from 'node-dependency-injection'

let definition = container.register('app.decorating_mailer', DecoratingMailer)
definition.decoratedService = 'app.mailer'
definition.addArgument(new Reference('app.decorating_mailer.inner'))
definition.public = false

container.compile()

Here 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.

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.

The generated code will be the following:

let mailerService = new DecoratingMailer(new Mailer()));

Remeber compile the container to decorate definitions

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).

YAML

services:
  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']

JS

import {Reference} from 'node-dependency-injection';

container.register('foo', Foo)

let definition = container.register('bar', Bar)
definition.addArgument(new Reference('bar.inner'))
definition.public = false
definition.decoratedService = 'foo'
definition.decorationPriority = 5

let definition = container.register('baz', Baz)
definition.addArgument(new Reference('baz.inner'))
definition.public= false
definition.decoratedService = 'foo'
definition.decorationPriority = 1

The generated code will be the following:

let fooService = new Baz(new Bar(new Foo())));