Extending Action Argument Resolving

Built-In Value Resolvers

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

BackedEnumValueResolver

Attempts to resolve a backed enum case from a route path parameter that matches the name of the argument. Leads to a 404 Not Found response if the value isn't a valid backing value for the enum type.

For example, if your backed enum is:

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namespace App\Model;

enum Suit: string
{
    case Hearts = 'H';
    case Diamonds = 'D';
    case Clubs = 'C';
    case Spades = 'S';
}

And your controller contains the following:

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class CardController
{
    #[Route('/cards/{suit}')]
    public function list(Suit $suit): Response
    {
        // ...
    }

    // ...
}

When requesting the /cards/H URL, the $suit variable will store the Suit::Hearts case.

Furthermore, you can limit route parameter's allowed values to only one (or more) with EnumRequirement:

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use Symfony\Component\Routing\Requirement\EnumRequirement;

// ...

class CardController
{
    #[Route('/cards/{suit}', requirements: [
        // this allows all values defined in the Enum
        'suit' => new EnumRequirement(Suit::class),
        // this restricts the possible values to the Enum values listed here
        'suit' => new EnumRequirement([Suit::Diamonds, Suit::Spades]),
    ])]
    public function list(Suit $suit): Response
    {
        // ...
    }

    // ...
}

The example above allows requesting only /cards/D and /cards/S URLs and leads to 404 Not Found response in two other cases.

RequestPayloadValueResolver

Maps the request payload or the query string into the type-hinted object.

Because this is a targeted value resolver, you'll have to use either the MapRequestPayload or the MapQueryString attribute in order to use this resolver.

RequestAttributeValueResolver

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

DateTimeValueResolver

Attempts to find a request attribute that matches the name of the argument and injects a DateTimeInterface object if type-hinted with a class extending DateTimeInterface.

By default any input that can be parsed as a date string by PHP is accepted. You can restrict how the input can be formatted with the MapDateTime attribute.

Tip

The DateTimeInterface object is generated with the Clock component. This gives you full control over the date and time values the controller receives when testing your application and using the MockClock implementation.

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 implementing SessionInterface if type-hinted with SessionInterface or a class implementing SessionInterface.

DefaultValueResolver

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

UidValueResolver

Attempts to convert any UID values from a route path parameter into UID objects. Leads to a 404 Not Found response if the value isn't a valid UID.

For example, the following will convert the token parameter into a UuidV4 object:

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// src/Controller/DefaultController.php
namespace App\Controller;

use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\Routing\Attribute\Route;
use Symfony\Component\Uid\UuidV4;

class DefaultController
{
    #[Route('/share/{token}')]
    public function share(UuidV4 $token): Response
    {
        // ...
    }
}

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, bridges and official bundles provide other value resolvers:

UserValueResolver

Injects the object that represents the current logged in user if type-hinted with UserInterface. You can also type-hint your own User class but you must then add the #[CurrentUser] attribute to the argument. Default value can be set to null in case the controller can be accessed by anonymous users. It requires installing the SecurityBundle.

If the argument is not nullable and there is no logged in user or the logged in user has a user class not matching the type-hinted class, an AccessDeniedException is thrown by the resolver to prevent access to the controller.

SecurityTokenValueResolver

Injects the object that represents the current logged in token if type-hinted with TokenInterface or a class extending it.

If the argument is not nullable and there is no logged in token, an HttpException with status code 401 is thrown by the resolver to prevent access to the controller.

EntityValueResolver

Automatically query for an entity and pass it as an argument to your controller.

For example, the following will query the Product entity which has {id} as primary key:

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// src/Controller/DefaultController.php
namespace App\Controller;

use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\Routing\Attribute\Route;

class DefaultController
{
    #[Route('/product/{id}')]
    public function share(Product $product): Response
    {
        // ...
    }
}

To learn more about the use of the EntityValueResolver, see the dedicated section Automatically Fetching Objects.

PSR-7 Objects Resolver:

Injects a Symfony HttpFoundation Request object created from a PSR-7 object of type Psr\Http\Message\ServerRequestInterface, Psr\Http\Message\RequestInterface or Psr\Http\Message\MessageInterface. It requires installing the PSR-7 Bridge component.

Managing Value Resolvers

For each argument, every resolver tagged with controller.argument_value_resolver will be called until one provides a value. The order in which they are called depends on their priority. For example, the SessionValueResolver will be called before the DefaultValueResolver because its priority is higher. This allows to write e.g. SessionInterface $session = null to get the session if there is one, or null if there is none.

In that specific case, you don't need any resolver running before SessionValueResolver, so skipping them would not only improve performance, but also prevent one of them providing a value before SessionValueResolver has a chance to.

The ValueResolver attribute lets you do this by "targeting" the resolver you want:

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// src/Controller/SessionController.php
namespace App\Controller;

use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpFoundation\Session\SessionInterface;
use Symfony\Component\HttpKernel\Attribute\ValueResolver;
use Symfony\Component\HttpKernel\Controller\ArgumentResolver\SessionValueResolver;
use Symfony\Component\Routing\Attribute\Route;

class SessionController
{
    #[Route('/')]
    public function __invoke(
        #[ValueResolver(SessionValueResolver::class)]
        SessionInterface $session = null
    ): Response
    {
        // ...
    }
}

In the example above, the SessionValueResolver will be called first because it is targeted. The DefaultValueResolver will be called next if no value has been provided; that's why you can assign null as $session's default value.

You can target a resolver by passing its name as ValueResolver's first argument. For convenience, built-in resolvers' name are their FQCN.

A targeted resolver can also be disabled by passing ValueResolver's $disabled argument to true; this is how MapEntity allows to disable the EntityValueResolver for a specific controller. Yes, MapEntity extends ValueResolver!

Adding a Custom Value Resolver

In the next example, you'll create a value resolver to inject an ID value object whenever a controller argument has a type implementing IdentifierInterface (e.g. BookingId):

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// src/Controller/BookingController.php
namespace App\Controller;

use App\Reservation\BookingId;
use Symfony\Component\HttpFoundation\Response;

class BookingController
{
    public function index(BookingId $id): Response
    {
        // ... do something with $id
    }
}

Adding a new value resolver requires creating a class that implements ValueResolverInterface and defining a service for it.

This interface contains a resolve() method, which is called for each argument of the controller. It receives the current Request object and an ArgumentMetadata instance, which contains all information from the method signature.

The resolve() method should return either an empty array (if it cannot resolve this argument) or an array with the resolved value(s). Usually arguments are resolved as a single value, but variadic arguments require resolving multiple values. That's why you must always return an array, even for single values:

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// src/ValueResolver/IdentifierValueResolver.php
namespace App\ValueResolver;

use App\IdentifierInterface;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpKernel\Controller\ValueResolverInterface;
use Symfony\Component\HttpKernel\ControllerMetadata\ArgumentMetadata;

class BookingIdValueResolver implements ValueResolverInterface
{
    public function resolve(Request $request, ArgumentMetadata $argument): iterable
    {
        // get the argument type (e.g. BookingId)
        $argumentType = $argument->getType();
        if (
            !$argumentType
            || !is_subclass_of($argumentType, IdentifierInterface::class, true)
        ) {
            return [];
        }

        // get the value from the request, based on the argument name
        $value = $request->attributes->get($argument->getName());
        if (!is_string($value)) {
            return [];
        }

        // create and return the value object
        return [$argumentType::fromString($value)];
    }
}

This method first checks whether it can resolve the value:

• The argument must be type-hinted with a class implementing a custom IdentifierInterface;
• The argument name (e.g. $id) must match the name of a request attribute (e.g. using a /booking/{id} route placeholder).

When those requirements are met, the method creates a new instance of the custom value object and returns it as the value for this argument.

That's it! Now all you have to do is add the configuration for the service container. This can be done by adding one of the following tags to your value resolver.

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

    App\ValueResolver\BookingIdValueResolver:
        tags:
            - controller.argument_value_resolver:
                name: booking_id
                priority: 150

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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\ValueResolver\BookingIdValueResolver">
            <tag name="booking_id" priority="150">controller.argument_value_resolver</tag>
        </service>
    </services>

</container>

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// config/services.php
namespace Symfony\Component\DependencyInjection\Loader\Configurator;

use App\ValueResolver\BookingIdValueResolver;

return static function (ContainerConfigurator $containerConfigurator): void {
    $services = $containerConfigurator->services();

    $services->set(BookingIdValueResolver::class)
        ->tag('controller.argument_value_resolver', ['name' => 'booking_id', 'priority' => 150])
    ;
};

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$ php bin/console debug:container debug.argument_resolver.inner --show-arguments

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// src/ValueResolver/IdentifierValueResolver.php
namespace App\ValueResolver;

use Symfony\Component\HttpKernel\Attribute\AsTargetedValueResolver;
use Symfony\Component\HttpKernel\Controller\ValueResolverInterface;

#[AsTargetedValueResolver('booking_id')]
class BookingIdValueResolver implements ValueResolverInterface
{
    // ...
}

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// src/Controller/BookingController.php
namespace App\Controller;

use App\Reservation\BookingId;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpKernel\Attribute\ValueResolver;

class BookingController
{
    public function index(#[ValueResolver('booking_id')] BookingId $id): Response
    {
        // ... do something with $id
    }
}