Built-In Value Resolvers

Symfony ships with the following value resolvers in the HttpKernel component:

RequestAttributeValueResolver

Attempts to find a request attribute that matches the name of the argument.

RequestValueResolver

Injects the current Request if type-hinted with Request or a class extending Request.

ServiceValueResolver

Injects a service if type-hinted with a valid service class or interface. This works like autowiring.

SessionValueResolver

Injects the configured session class extending SessionInterface if type-hinted with SessionInterface or a class extending SessionInterface.

DefaultValueResolver

Will set the default value of the argument if present and the argument is optional.

VariadicValueResolver

Verifies if the request data is an array and will add all of them to the argument list. When the action is called, the last (variadic) argument will contain all the values of this array.

In addition, some components and official bundles provide other value resolvers:

UserValueResolver

Injects the object that represents the current logged in user if type-hinted with UserInterface. Default value can be set to null in case the controller can be accessed by anonymous users. It requires installing the Security component.

SecurityUserValueResolver

Injects the object that represents the current logged in user if type-hinted with UserInterface. Default value can be set to null in case the controller can be accessed by anonymous users. It requires installing the SecurityBundle.

Psr7ServerRequestResolver

Injects a PSR-7 compliant version of the current request if type-hinted with RequestInterface, MessageInterface or ServerRequestInterface. It requires installing the SensioFrameworkExtraBundle.

Adding a Custom Value Resolver

In the next example, you'll create a value resolver to inject the object that represents the current user whenever a controller method type-hints an argument with the User class:

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namespace App\Controller;

use App\Entity\User;
use Symfony\Component\HttpFoundation\Response;

class UserController
{
    public function index(User $user)
    {
        return new Response('Hello '.$user->getUsername().'!');
    }
}

Beware that this feature is already provided by the @ParamConverter annotation from the SensioFrameworkExtraBundle. If you have that bundle installed in your project, add this config to disable the auto-conversion of type-hinted method arguments:

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# config/packages/sensio_framework_extra.yaml
sensio_framework_extra:
    request:
        converters: true
        auto_convert: false

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<!-- config/packages/sensio_framework_extra.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"
    xmlns:sensio-framework-extra="http://symfony.com/schema/dic/symfony_extra"
    xsi:schemaLocation="http://symfony.com/schema/dic/services
        https://symfony.com/schema/dic/services/services-1.0.xsd">

    <sensio-framework-extra:config>
        <request converters="true" auto-convert="false"/>
    </sensio-framework-extra:config>
</container>

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// config/packages/sensio_framework_extra.php
$container->loadFromExtension('sensio_framework_extra', [
    'request' => [
        'converters' => true,
        'auto_convert' => false,
    ],
]);

Adding a new value resolver requires creating a class that implements ArgumentValueResolverInterface and defining a service for it. The interface defines two methods:

supports()

This method is used to check whether the value resolver supports the given argument. resolve() will only be executed when this returns true.

resolve()

This method will resolve the actual value for the argument. Once the value is resolved, you must yield the value to the ArgumentResolver.

Both methods get the Request object, which is the current request, and an ArgumentMetadata instance. This object contains all information retrieved from the method signature for the current argument.

Now that you know what to do, you can implement this interface. To get the current User, you need the current security token. This token can be retrieved from the token storage:

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// src/ArgumentResolver/UserValueResolver.php
namespace App\ArgumentResolver;

use App\Entity\User;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpKernel\Controller\ArgumentValueResolverInterface;
use Symfony\Component\HttpKernel\ControllerMetadata\ArgumentMetadata;
use Symfony\Component\Security\Core\Security;

class UserValueResolver implements ArgumentValueResolverInterface
{
    private $security;

    public function __construct(Security $security)
    {
        $this->security = $security;
    }

    public function supports(Request $request, ArgumentMetadata $argument)
    {
        if (User::class !== $argument->getType()) {
            return false;
        }

        return $this->security->getUser() instanceof User;
    }

    public function resolve(Request $request, ArgumentMetadata $argument)
    {
        yield $this->security->getUser();
    }
}

In order to get the actual User object in your argument, the given value must fulfill the following requirements:

• An argument must be type-hinted as User in your action method signature;
• The value must be an instance of the User class.

When all those requirements are met and true is returned, the ArgumentResolver calls resolve() with the same values as it called supports().

That's it! Now all you have to do is add the configuration for the service container. This can be done by tagging the service with controller.argument_value_resolver and adding a priority.

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# config/services.yaml
services:
    _defaults:
        # ... be sure autowiring is enabled
        autowire: true
    # ...

    App\ArgumentResolver\UserValueResolver:
        tags:
            - { name: controller.argument_value_resolver, priority: 50 }

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<!-- 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 https://symfony.com/schema/dic/services/services-1.0.xsd">

    <services>
        <!-- ... be sure autowiring is enabled -->
        <defaults autowire="true"/>
        <!-- ... -->

        <service id="App\ArgumentResolver\UserValueResolver">
            <tag name="controller.argument_value_resolver" priority="50"/>
        </service>
    </services>

</container>

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// config/services.php
use App\ArgumentResolver\UserValueResolver;

$container->autowire(UserValueResolver::class)
    ->addTag('controller.argument_value_resolver', ['priority' => 50]);

While adding a priority is optional, it's recommended to add one to make sure the expected value is injected. The RequestAttributeValueResolver has a priority of 100. As this one is responsible for fetching attributes from the Request, it's recommended to trigger your custom value resolver with a lower priority. This makes sure the argument resolvers are not triggered when the attribute is present. For instance, when passing the user along a subrequests.