Querying posts by custom field with WPGraphQL

[NazarTikhoniuk]

Greetings!
I have a question about querying posts of models created with Atlas Content Modeler with WPGraphQL.
WPGraphQL has an option to query posts by global ID, database ID, URI and slug - https://www.wpgraphql.com/docs/posts-and-pages/#querying-posts
Are there any options to query posts by custom field value of the model?
Thanks!

[nickcernis]

Thanks for your question, Nazar.

Atlas Content Modeler does not support 'where' queries for field values via WPGraphQL by default.

If you need this feature now, you would have to write some custom PHP code following a guide like this one for ACF. The example adds support for the 'where' argument for a named ACF field that appears on the core Post type. It could be adapted for ACM's fields and custom post types.

Note that altering WPGraphQL or ACM behavior with custom code carries some risks (your code could break after updates to WPGraphQL or ACM), but here's a quick example if you want to explore it further:

• You have a 'Rabbits' ACM model.
• Rabbits has a text field called 'color'.
• You want to be able run queries similar to get rabbits where color = 'black'.

This PHP code in your active theme's functions.php (or in a custom plugin) enables that:

add_action( 'graphql_register_types', 'custom_acm_register_where_query' );
function custom_acm_register_where_query() {
	$acm_model_graphql_singular_name = 'Rabbit';
	$acm_field_name                  = 'color';

	register_graphql_field(
		'RootQueryTo' . $acm_model_graphql_singular_name . 'ConnectionWhereArgs',
		$acm_field_name,
		[
			'type'        => 'String',
			'description' => __( 'The color of the rabbit to filter by', 'your-textdomain' ),
		]
	);
}

add_filter( 'graphql_post_object_connection_query_args', 'custom_acm_filter_connection_query', 10, 3 );
function custom_acm_filter_connection_query( $query_args, $source, $args ) {
	$acm_field_name = 'color';

	$where_query_value = $args['where'][$acm_field_name];

	if ( isset( $where_query_value) ) {
		$query_args['meta_query'] = [
			[
				'key'     => $acm_field_name,
				'value'   => $where_query_value,
				'compare' => '='
			]
		];
	}

	return $query_args;
}

Allowing you to do queries like:

query RabbitsByColor {
  rabbits(where: {color: "black"}) {
    nodes {
      databaseId
    }
  }
}

And get the IDs of the two black rabbits in response:

{
  "data": {
    "rabbits": {
      "nodes": [
        {
          "databaseId": 4211
        },
        {
          "databaseId": 4209
        }
      ]
    }
  }
}

[nickcernis]

Just to add that an alternative to querying by custom field values is to set up taxonomies for your models and write queries for those. This requires an extra plugin called WPGraphQL Tax Query but no custom code.

ACM already supports custom taxonomies:

https://developers.wpengine.com/docs/atlas-content-modeler/tutorial/models/taxonomies/create

WPGraphQL Taxonomy queries with ACM are documented here:

https://developers.wpengine.com/docs/atlas-content-modeler/tutorial/models/taxonomies/query

Taxonomy queries are often faster than field value queries too.