Routes

A very powerful feature of Drupal is the ability to manage paths in entities and using path alias to manage clean URL's. We can leverage Data producers provided by the GraphQL module to get that data out of Drupal.

In this section we will look at how we can load a node from it's URL.

Add the schema declaration

The first step as seen in the introduction is to add the types and fields in the schema. We can do this directly in the schema string in your own schema implementation.

...

type Query {
    route(path: String!): NodeInterface
}

type Article implements NodeInterface {
    id: Int!
    uid: String
    title: String!
}

interface NodeInterface {
    id: Int!
}

...

In this schema we can see that we can query a node by its route, that takes a parameter called "path". We also (similar to the test schema that comes with the module) have a NodeInterface and a Article type that implements that interface. That means our "Article" will be available inside a fragment in the NodeInterface type.

Adding resolvers

To add the resolvers we go to our schema implementation and call the appropriate data producers inside the getResolverRegistry method.

/**
   * {@inheritdoc}
   */
  protected function getResolverRegistry() {
    ...

    $registry->addFieldResolver('Query', 'route', $builder->compose(
      $builder->produce('route_load', [
        'mapping' => [
          'path' => $builder->fromArgument('path'),
        ],
      ]),
      $builder->produce('route_entity', [
        'mapping' => [
          'url' => $builder->fromParent(),
        ],
      ])
    ));

    ...

    return $registry;
  }

Here we take advantage of the compose method inside our resolver builder object that allows chaining multiple producers together. This is a very useful technique, that will be very useful when dealing with more complex scenarios.

In this example our query could look like this :

{
  route(path: "/node/1") {
    ... on Article {
      id
      title
    }
  }
}

and the response :

{
  "data": {
    "route": {
      "id": 1,
      "title": "Hello GraphQL"
    }
  }
}