The GraphQL Query Language

On this page, we'll explore various various features of the GraphQL Query Language

This page is setup as a progression, showing basic usage of GraphQL queries, to more advanced queries and features of the GraphQL query language

Hello World

This is essentially the "hello world" of GraphQL Queries. Here, we are just asking the site for it's Title and URL. Basic settings almost any application built on top of WordPress would need.

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Posts

At the heart of WordPress are Posts. Out of the box, WPGraphQL provides general Schema setup for interacting with posts.

Collection of Posts

Here's an example of querying for a list of posts. By default, you will get 10 posts back.

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What's with the different IDs?

You may have noticed that we asked for both an id and postId field.

The id field is a Global ID that is unique to just that object. In WordPress, many objects can have the same id. For example, a comment can have id 1, a post can have id 1, a taxonomy term can have id 1.

The ID field in WPGraphQL is a hash of the Type of content it is and it's integer ID, making it unique across all Types.

Single Post

If you know the ID of a particular Post, you can query for an individual Post, like so:

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PostBy

Sometimes, you may need to fetch an individual Post, but you don't know the ID, but have some other identifier, such as the slug or the uri.

In that case, we can use a postBy query to fetch using the slug:

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Pages

Pages are exposed to WPGraphQL as well, and can be queried in a similar fashion to Posts.

Collections of Pages

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Single Page

If we know the Global ID of a page, we can query for it like so:

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PageBy

Since pages are hierarchical, many pages can have the same slug, so we can't reliably use a slug as an identifier and thus there's no option to query a pageBy using the slug field in the same way non-hierarchical Post Types can be queried. However, if we know the URI, we can that as a unique identifier to fetch an individual Page.

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Custom Post Types

WPGraphQL allows for Custom Post Types to be shown in the GraphQL Schema by registering support in the Post Type registry.

There are 3 fields that need to be defined to have a Custom Post Type show in GraphQL:

  • show_in_graphql: true or false
  • graphql_single_name: camel case string with no punctuation or spaces
  • graphql_plural_name: camel case string with no punctuation or spaces

Registering a new Post Type

If you control the code for the Post Type being registered, you can add these three fields to the code that registers your Post Type.

For example, here's an example that registers a Custom Post Type called docs and sets it to show in GraphQL:

add_action( 'init', function() {
   register_post_type( 'docs', [
      'show_in_graphql' => true,
      'hierarchical' => true,
      'graphql_single_name' => 'Document',
      'graphql_plural_name' => Documents',
   ] );
} );

Filter Existing Post Type

If you want to expose a Post Type that you don't directly control the registration for, such as a Post Type registerted in a third-party plugin, you can filter the Post Type registration like so:

add_filter( 'register_post_type_args', function( $args, $post_type ) {

    if ( 'docs' === $post_type ) {
        $args['show_in_graphql'] = true;
        $args['graphql_single_name'] = 'Document';
        $args['graphql_plural_name'] = 'Documents';
    }

    return $args;

}, 10, 2 );

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