How to Inject Values Based on Complex Expressions
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How to Inject Values Based on Complex Expressions
The service container also supports an "expression" that allows you to inject very specific values into a service.
For example, suppose you have a service (not shown here), called App\Mail\MailerConfiguration,
which has a getMailerMethod() method on it. This returns a string - like sendmail
based on some configuration.
Suppose that you want to pass the result of this method as a constructor argument
to another service: App\Mailer. One way to do this is with an expression:
- YAML
- XML
- PHP
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# config/services.yaml
services:
# ...
App\Mail\MailerConfiguration: ~
App\Mailer:
arguments: ["@=service('App\\\\Mail\\\\MailerConfiguration').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:
- YAML
- XML
- PHP
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# config/services.yaml
services:
App\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).
