symfony · linaori · Apr 6, 2016 · Apr 6, 2016 · Apr 6, 2016 · Apr 6, 2016
diff --git a/cookbook/controller/argument_value_resolver.rst b/cookbook/controller/argument_value_resolver.rst
@@ -0,0 +1,234 @@
+.. index::
+   single: Controller; Argument Value Resolvers
+
+Extending Action Argument Resolving
+===================================
+
+.. versionadded:: 3.1
+    The ``ArgumentResolver`` and value resolvers were introduced in Symfony 3.1.
+
+In the book, you've learned that you can get the :class:`Symfony\\Component\\HttpFoundation\\Request`
+object via an argument in your controller. This argument has to be typehinted
+by the ``Request`` class in order to be recognized. This is done via the
+:class:`Symfony\\Component\\HttpKernel\\Controller\\ArgumentResolver`. By
+creating and registering custom argument value resolvers, you can extend
+this functionality.
+
+Functionality Shipped With The HttpKernel
+-----------------------------------------
+
+Symfony ships with four value resolvers in the HttpKernel:
+
+:class:`Symfony\\Component\\HttpKernel\\Controller\\ArgumentValueResolver\\ArgumentFromAttributeResolver`
+    Attempts to find a request attribute that matches the name of the argument.
+
+:class:`Symfony\\Component\\HttpKernel\\Controller\\ArgumentValueResolver\\RequestValueResolver`
+    Injects the current ``Request`` if type-hinted with ``Request``, or a
+    sub-class thereof.
+
+:class:`Symfony\\Component\\HttpKernel\\Controller\\ArgumentValueResolver\\DefaultValueResolver`
+    Will set the default value of the argument if present and the argument
+    is optional.
+
+:class:`Symfony\\Component\\HttpKernel\\Controller\\ArgumentValueResolver\\VariadicValueResolver`
+    Verifies in the request if your 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.
+
+.. note::
+
+    Prior to Symfony 3.1, this logic was resolved within the ``ControllerResolver``.
+    The old functionality is rewritten to the aforementioned value resolvers.
+
+Adding a Custom Value Resolver
+------------------------------
+
+Adding a new value resolver requires one class and one service defintion.
+In the next example, you'll create a value resolver to inject the ``User``
+object from the security system. Given you write the following action::
+
+    namespace AppBundle\Controller;
+
+    use AppBundle\Entity\User;
+    use Symfony\Component\HttpFoundation\Response;
+
+    class UserController
+    {
+        public function indexAction(User $user)
+        {
+            return new Response('<html><body>Hello '.$user->getUsername().'!</body></html>');
+        }
+    }
+
+Somehow you will have to get the ``User`` object and inject it into the controller.
+This can be done by implementing the :class:`Symfony\\Component\\HttpKernel\\Controller\\ArgumentValueResolverInterface`.
+This interface specifies that you have to implement two methods::
+
+    interface ArgumentValueResolverInterface
+    {
+        public function supports(Request $request, ArgumentMetadata $argument);
+        public function resolve(Request $request, ArgumentMetadata $argument);
+    }
+
+``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
+:class:`Symfony\\Component\\HttpKernel\\ControllerMetadata\\ArgumentMetadata`.
+This object contains all information retrieved from the method signature for
+the current argument.
+
+.. note::
+
+    The ``ArgumentMetadata`` is a simple data container created by the
+    :class:`Symfony\\Component\\HttpKernel\\ControllerMetadata\\ArgumentMetadataFactory`.
+    This factory will work on every supported PHP version but might give
+    different results. E.g. the ``isVariadic()`` will never return true on
+    PHP 5.5 and only on PHP 7.0 and higher it will give you basic types when
+    calling ``getType()``.
+
+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::
+
+    namespace AppBundle\ArgumentValueResolver;
+
+    use AppBundle\Entity\User;
+    use Symfony\Component\HttpKernel\Controller\ArgumentValueResolverInterface;
+    use Symfony\Component\Security\Core\Authentication\Token\Storage\TokenStorageInterface;
+
+    class UserValueResolver implements ArgumentValueResolverInterface
+    {
+        private $tokenStorage;
+
+        public function __construct(TokenStorageInterface $tokenStorage)
+        {
+            $this->tokenStorage = $tokenStorage;
+        }
+
+        public function supports(Request $request, ArgumentMetadata $argument)
+        {
+            if (User::class !== $argument->getType()) {
+                return false;
+            }
+
+            $token = $this->tokenStorage->getToken();
+
+            if (!$token instanceof TokenInterface) {
+                return false;
+            }
+
+            return $token->getUser() instanceof User;
+        }
+
+        public function resolve(Request $request, ArgumentMetadata $argument)
+        {
+            yield $this->tokenStorage->getToken()->getUser();
+        }
+    }
+
+In order to get the actual ``User`` object in your argument, the given value
+must fulfill the following requirements:
+
+* An argument must be typehinted as ``User`` in your action method signature;
+* A security token must be present;
+* The value must be an instance of the ``User``.
+
+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 ``kernel.argument_resolver``
+and adding a priority.
+
+.. note::
+
+    While adding a priority is optional, it's recommended to add one to
+    make sure the expected value is injected. The ``ArgumentFromAttributeResolver``
+    has a priority of 100. As this one is responsible for fetching attributes
+    from the ``Request``, it's also recommended to trigger your custom value
+    resolver with a lower priority. This makes sure the argument resolvers
+    are not triggered in (e.g.) subrequests if you pass your user along:
+    ``{{ render(controller('AppBundle:User:index', {'user', app.user})) }}``.
+
+.. configuration-block::
+
+    .. code-block:: yaml
+
+        # app/config/services.yml
+        services:
+            app.value_resolver.user:
+                class: AppBundle\ArgumentValueResolver\UserValueResolver
+                arguments:
+                    - '@security.token_storage'
+                tags:
+                    - { name: controller.argument_value_resolver, priority: 50 }
+
+    .. code-block:: xml
+
+        <!-- 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="app.value_resolver.user" class="AppBundle\ArgumentValueResolver\UserValueResolver">
+                    <argument type="service" id="security.token_storage">
+                    <tag name="controller.argument_value_resolver" priority="50" />
+                </service>
+            </services>
+
+        </container>
+
+    .. code-block:: php
+
+        // app/config/services.php
+        use Symfony\Component\DependencyInjection\Definition;
+
+        $defintion = new Definition(
+            'AppBundle\ArgumentValueResolver\UserValueResolver',
+            array(new Reference('security.token_storage'))
+        );
+        $definition->addTag('controller.argument_value_resolver', array('priority' => 50));
+        $container->setDefinition('app.value_resolver.user', $definition);
+
+Creating an Optional User Resolver
+----------------------------------
+
+When you want your user to be optional, e.g. when your page is behind a
+firewall that also allows anonymous authentication, you might not always
+have a security user. To get this to work, you only have to change your
+method signature to `UserInterface $user = null`.
+
+When you take the ``UserValueResolver`` from the previous example, you can
+see there is no logic in case of failure to comply to the requirements. Default
+values are defined in the signature and are available in the ``ArgumentMetadata``.
+When a default value is available and there are no resolvers that support
+the given value, the ``DefaultValueResolver`` is triggered. This Resolver
+takes the default value of your argument and yields it to the argument list::
+
+    namespace Symfony\Component\HttpKernel\Controller\ArgumentResolver;
+
+    use Symfony\Component\HttpFoundation\Request;
+    use Symfony\Component\HttpKernel\Controller\ArgumentValueResolverInterface;
+    use Symfony\Component\HttpKernel\ControllerMetadata\ArgumentMetadata;
+
+    final class DefaultValueResolver implements ArgumentValueResolverInterface
+    {
+        public function supports(Request $request, ArgumentMetadata $argument)
+        {
+            return $argument->hasDefaultValue();
+        }
+
+        public function resolve(Request $request, ArgumentMetadata $argument)
+        {
+            yield $argument->getDefaultValue();
+        }
+    }
+
+.. _`yield`: http://php.net/manual/en/language.generators.syntax.php
diff --git a/cookbook/controller/index.rst b/cookbook/controller/index.rst
@@ -7,3 +7,4 @@ Controller
     error_pages
     service
     upload_file
+    argument_value_resolver
diff --git a/cookbook/map.rst.inc b/cookbook/map.rst.inc
@@ -56,6 +56,7 @@
   * :doc:`/cookbook/controller/error_pages`
   * :doc:`/cookbook/controller/service`
   * :doc:`/cookbook/controller/upload_file`
+  * :doc:`/cookbook/controller/argument_value_resolver`
 
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