Paris 2019 March 28-29

  1. Home
  2. Documentation
  3. Service Container
  4. How to Inject Values Based on Complex Expressions

How to Inject Values Based on Complex Expressions

3.4 version
Maintained
2.8 4.1 current 4.2 master
Unmaintained
2.7 3.0 3.1 3.2 3.3 4.0
edit this page

How to Inject Values Based on Complex ExpressionsΒΆ

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 AppBundle\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: AppBundle\Mailer. One way to do this is with an expression:

  • YAML
    1
2
3
4
5
6
7
8
    # app/config/services.yml
services:
    # ...

    AppBundle\Mail\MailerConfiguration: ~

    AppBundle\Mailer:
        arguments: ["@=service('AppBundle\\\\Mail\\\\MailerConfiguration').getMailerMethod()"]
  • XML
     1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
    <!-- app/config/services.xml -->
<?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="AppBundle\Mail\MailerConfiguration"></service>

        <service id="AppBundle\Mailer">
            <argument type="expression">service('App\\Mail\\MailerConfiguration').getMailerMethod()</argument>
        </service>
    </services>
</container>
  • PHP
    1
2
3
4
5
6
7
8
9
    // app/config/services.php
use AppBundle\Mail\MailerConfiguration;
use AppBundle\Mailer;
use Symfony\Component\ExpressionLanguage\Expression;

$container->autowire(MailerConfiguration::class);

$container->autowire(Mailer::class)
    ->addArgument(new Expression('service("AppBundle\\\\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
    1
2
3
    services:
    AppBundle\Mailer:
        arguments: ["@=container.hasParameter('some_param') ? parameter('some_param') : 'default_value'"]
  • XML
     1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
    <?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="AppBundle\Mailer">
            <argument type="expression">container.hasParameter('some_param') ? parameter('some_param') : 'default_value'</argument>
        </service>
    </services>
</container>
  • PHP
    1
2
3
4
5
6
7
    use AppBundle\Mailer;
use Symfony\Component\ExpressionLanguage\Expression;

$container->autowire(Mailer::class)
    ->addArgument(new Expression(
        "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).

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.