index.md

Events

Events are a way to hook into the execution flow. This bundle provides various events from executor and context value initialization, executor result formatting (data, errors, extensions), errors/warnings formatting.

With this in mind we now turn to explain each one of them.

Executor context value

Event: graphql.executor.context

This event can be listen to initialize executor contextValue argument.

Executor initialisation

Event: graphql.pre_executor

This event can be listen to initialize executor execute arguments (schema, requestString, rootValue, contextValue, variableValue, operationName).

For example:

• Initializing rootValue with the current user (we assume that user is fully authenticated)

  App\EventListener\RootValueInitialization:
      tags:
          - { name: kernel.event_listener, event: graphql.pre_executor, method: onPreExecutor }

  <?php
  
  namespace App\EventListener;
  
  use Overblog\GraphQLBundle\Event\ExecutorArgumentsEvent;
  use Symfony\Component\Security\Core\Authentication\Token\TokenInterface;
  
  class RootValueInitialization
  {
    private $token;
  
    public function __construct(TokenInterface $token)
    {
         $this->token = $token;
    }
  
    public function onPreExecutor(ExecutorArgumentsEvent $event)
    {
        $event->setRootValue($this->token->getUser());
    }
  }

Executor result

Event: graphql.post_executor

This event can be listen to set custom error handling and formatting, it can also be use to add information to extensions section.

For example:

• How to add credits entry in extensions section

  App\EventListener\Credits:
      tags:
          - { name: kernel.event_listener, event: graphql.post_executor, method: onPostExecutor }

  <?php
  
  namespace App\EventListener;
  
  use Overblog\GraphQLBundle\Event\ExecutorResultEvent;
  
  class Credits
  {
    public function onPostExecutor(ExecutorResultEvent $event)
    {
        $event->getResult()->extensions['credits'] = 'This api was powered by "OverblogGraphQLBundle".';
    }
  }

  result: