one-to-one-connections-helping-emiliano.php

add_action( 'graphql_register_types', function() {

	$post_types = WPGraphQL::$allowed_post_types;

	if ( ! empty( $post_types ) && is_array( $post_types ) ) {
		foreach ( $post_types as $post_type ) {
			$post_type_object = get_post_type_object( $post_type );

			/**
			 * Get the Type name with ucfirst
			 */
			$ucfirst = ucfirst( $post_type_object->graphql_single_name );

			/**
			 * Register a new Edge Type
			 */
			register_graphql_type( 'Next' . $ucfirst . 'Edge', [
				'fields' => [
					'node' => [
						'description' => __( 'The node of the next item', 'wp-graphql' ),
						'type' => $ucfirst,
					],
				],
			] );

			/**
			 * Register the next{$type} field
			 */
			register_graphql_field( $ucfirst, 'next' . $ucfirst, [
				'type'        => 'Next' . $ucfirst . 'Edge',
				'description' => __( 'The next post of the current port', 'wp-graphql' ),
				'resolve'     => function( $resolving_post, $args, $context ) {
					$resolving_post = get_post( $resolving_post->postId );
				    $GLOBALS['post'] = $resolving_post;
					setup_postdata( $resolving_post );
					$nextPost = get_next_post();
					$post_model = $nextPost ? new \WPGraphQL\Model\Post( $nextPost ) : null;
					$result   = [
						'node' => ! empty( $post_model ) ? $post_model : null,
					];
					return empty( $nextPost ) ? null : $result;
				}
			] );

			/**
			 * Register a new Edge Type
			 */
			register_graphql_type( 'Previous' . $ucfirst . 'Edge', [
				'fields' => [
					'node' => [
						'description' => __( 'The node of the previous item', 'wp-graphql' ),
						'type' => $ucfirst,
					],
				],
			] );

			/**
			 * Register the next{$type} field
			 */
			register_graphql_field( $ucfirst, 'previous' . $ucfirst, [
				'type'        => 'Previous' . $ucfirst . 'Edge',
				'description' => __( 'The previous post of the current port', 'wp-graphql' ),
				'resolve'     => function( $resolving_post, $args, $context ) {
					$resolving_post = get_post( $resolving_post->postId );
					$GLOBALS['post'] = $resolving_post;
					setup_postdata( $resolving_post );
					$nextPost = get_previous_post();
					$post_model = $nextPost ? new \WPGraphQL\Model\Post( $nextPost ) : null;
					$result   = [
						'node' => ! empty( $post_model ) ? $post_model : null,
					];
					return empty( $nextPost ) ? null : $result;
				}
			] );

		}
	}

} );