resolver.md

Resolver

To ease development we named 2 types of resolver:

• Resolver that should be use for resolving readonly actions (query)
• Mutation that should be use for resolving writing actions (mutation)

This is just a recommendation.

Resolvers can be define 2 different ways

1. The PHP way

   You can declare a resolver (any class that implements Overblog\GraphQLBundle\Definition\Resolver\ResolverInterface or Overblog\GraphQLBundle\Definition\Resolver\MutationInterface) in src/*Bundle/GraphQL or app/GraphQL and they will be auto discovered. Auto map classes method are accessible by:

   • the class method name (example: AppBunble\GraphQL\CustomResolver::myMethod)
   • the FQCN for callable classes (example: AppBunble\GraphQL\InvokeResolver for a resolver implementing the __invoke method) you can also alias a type by implementing Overblog\GraphQLBundle\Definition\Resolver\AliasedInterface which returns a map of method/alias. The service created will autowire the __construct and Symfony\Component\DependencyInjection\ContainerAwareInterface::setContainer methods.

   Here an example:

   <?php
   
   namespace App\GraphQL\Resolver;
   
   use Overblog\GraphQLBundle\Definition\Resolver\AliasedInterface;
   use Overblog\GraphQLBundle\Definition\Resolver\ResolverInterface;
   
   class Greetings implements ResolverInterface, AliasedInterface
   {
       public function sayHello($name)
       {
           return sprintf('hello %s!!!', $name);
       }
   
       /**
        * {@inheritdoc}
        */
       public static function getAliases()
       {
           return ['sayHello' => 'say_hello'];
       }
   }

   SayHello resolver can be access by using App\GraphQL\Resolver\Greetings::sayHello or say_hello alias.

   we can also use class invoker:

   <?php
   
   namespace App\GraphQL\Resolver;
   
   use Overblog\GraphQLBundle\Definition\Resolver\ResolverInterface;
   
   class Greetings implements ResolverInterface
   {
       public function __invoke($name)
       {
           return sprintf('hello %s!!!', $name);
       }
   }

   This way SayHello resolver can be accessed with App\GraphQL\Resolver\Greetings.

   for mutation:

   <?php
   
   namespace App\GraphQL\Mutation;
   
   use Overblog\GraphQLBundle\Definition\Resolver\AliasedInterface;
   use Overblog\GraphQLBundle\Definition\Resolver\MutationInterface;
   
   class CalcMutation implements MutationInterface, AliasedInterface
   {
       private $value;
   
       public function addition($number)
       {
           $this->value += $number;
       }
   
       /**
        * {@inheritdoc}
        */
       public static function getAliases()
       {
           return ['addition' => 'add'];
       }
   }

   addition mutation can be access by using App\GraphQL\Mutation\CalcMutation::addition or add alias.

   You can also define custom dirs using the config:

   overblog_graphql:
       definitions:
           auto_mapping:
               directories:
                   - "%kernel.root_dir%/src/*Bundle/CustomDir"
                   - "%kernel.root_dir%/src/AppBundle/{foo,bar}"

   If using Symfony 3.3+ disabling auto mapping can be a solution to leave place to native DI autoconfigure:

   overblog_graphql:
       definitions:
           auto_mapping: false

   Here an example of how this can be done with DI autoconfigure:

   App\Mutation\:
       resource: '../src/Mutation'
       tags: ['overblog_graphql.mutation']
   
   App\Resolver\:
       resource: '../src/Resolver'
       tags: ['overblog_graphql.resolver']
   
   App\Type\:
       resource: '../src/Type'
       tags: ['overblog_graphql.type']

   Note:

   • When using FQCN in yaml definition, backslash must be correctly quotes, here an example '@=resolver("App\\GraphQL\\Resolver\\Greetings", [args['name']])'.

2. The service way

   Creating a service tagged overblog_graphql.resolver for resolvers or overblog_graphql.mutation for mutations.

   Using the php way examples:

   services:
       App\GraphQL\Resolver\Greetings:
           # only for sf < 3.3
           #class: App\GraphQL\Resolver\Greetings
           tags:
               - { name: overblog_graphql.resolver, method: sayHello, alias: say_hello } # add alias say_hello
               - { name: overblog_graphql.resolver, method: sayHello } # add method full qualified name

   SayHello resolver can be access by using App\GraphQL\Resolver\Greetings::sayHello or say_hello alias.

   for invokable classes no need to use alias and method attributes:

   services:
       App\GraphQL\Resolver\Greetings:
           # only for sf < 3.3
           #class: App\GraphQL\Resolver\Greetings
           tags:
               - { name: overblog_graphql.resolver }

   This way resolver can be accessed with FQCN App\GraphQL\Resolver\Greetings.

   for mutation:

   services:
       App\GraphQL\Mutation\CalcMutation:
           # only for sf < 3.3
           #class: App\GraphQL\Mutation\CalcMutation
           tags:
               - { name: overblog_graphql.mutation, method: addition, alias: add }

   addition mutation can be access by using App\GraphQL\Mutation\CalcMutation::addition or add alias.

Next step solving N+1 problem