How to Inject Values Based on Complex Expressions
Warning: You are browsing the documentation for Symfony 2.x, which is no longer maintained.
Read the updated version of this page for Symfony 7.2 (the current stable version).
The service container also supports an "expression" that allows you to inject very specific values into a service.
For example, suppose you have a third service (not shown here), called mailer_configuration,
which has a getMailerMethod() method on it, which will return a string
like sendmail based on some configuration. Remember that the first argument
to the my_mailer service is the simple string sendmail:
1 2 3 4 5
# app/config/services.yml
services:
app.mailer:
class: AppBundle\Mailer
arguments: [sendmail]But instead of hardcoding this, how could we get this value from the getMailerMethod()
of the new mailer_configuration service? One way is to use an expression:
1 2 3 4 5
# app/config/services.yml
services:
my_mailer:
class: AppBundle\Mailer
arguments: ["@=service('mailer_configuration').getMailerMethod()"]To learn more about the expression language syntax, see The Expression Syntax.
In this context, you have access to 2 functions:
service- Returns a given service (see the example above).
parameter-
Returns a specific parameter value (syntax is just like
service).
You also have access to the Container
via a container variable. Here's another example:
1 2 3 4
services:
my_mailer:
class: AppBundle\Mailer
arguments: ["@=container.hasParameter('some_param') ? parameter('some_param') : 'default_value'"]Expressions can be used in arguments, properties, as arguments with
configurator and as arguments to calls (method calls).