register_graphql_field

Add a field to a Type in the GraphQL Schema

register_graphql_field( string $type_name, string $field_name, array $config );

Parameters

• $type_name (string): The name of the GraphQL Type in the Schema to register the field to
• $field_name (string): The name of the field. Should be unique to the Type the field is being registered to.
• $config (array): Configuration for the field
  • $type (string | array): The name of the GraphQL Type the field will return. The resolve function must return this type.
    • For non-null fields: 'type' => [ 'non_null' => 'TypeName' ]
    • For listOf fields: 'type' => [ 'list_of' => 'TypeName' ]
  • $description (string): Description of the field. This will be used to self-document the schema and should describe to clients how the field should be used.
  • $resolve (function): Function that will execute when the field is asked for in a query.

Source

File: access-functions.php

Examples

Below are some examples of using the function to extend the GraphQL Schema.

Register a Root Field

This example adds a field to the root of the GraphQL Schema.

add_action( 'graphql_register_types', function() {
  register_graphql_field( 'RootQuery', 'testField', [
    'type' => 'String',
    'description' => __( 'Example field added to the RootQuery Type', 'replace-with-your-textdomain' ),
    'resolve' => function( $root, $args, $context, $info ) {
      return 'Example string.';
    }
  ] );
});

Example Query

{
  testField
}

Register a Post Field

This example shows how to register a field to the Post type.

add_action( 'graphql_register_types', function() {
  register_graphql_field( 'Post', 'testPostField', [
    'type' => 'String',
    'description' => __( 'Example field added to the Post Type', 'replace-with-your-textdomain' ),
    'resolve' => function( \WPGraphQL\Model\Post $post, $args, $context, $info ) {
      return 'Example string with the title of the post: ' . $post->titleRendered;
    }
  ] );
});

Example Query

{
  posts(first: 1) {
    nodes {
      title
      testPostField
    }
  }
}

Register a field to an Interface

This example shows how to register a field to an Interface. In this example, a field is registered to the “ContentNode” Interface. This means any Type (any WordPress Post Type) in the Schema that implements the “ContentNode” interface will have the field.

add_action( 'graphql_register_types', function() {
  register_graphql_field( 'ContentNode', 'testContentNodeField', [
    'type' => 'String',
    'description' => __( 'Example field added to the ContentNode Interface', 'replace-with-your-textdomain' ),
    'resolve' => function( \WPGraphQL\Model\Post $post_model, $args, $context, $info ) {
      return 'Example string with the title of the post: ' . $post->titleRendered;
    }
  ] );
});

Example Query:

{
  contentNodes(first: 2, where: {contentTypes: [PAGE, POST]}) {
    nodes {
      __typename
      id
      testContentNodeField
    }
  }
}