REST-API: extend media-endpoint

Question

I want to modify the REST-API (media-endpoint) and add a new field called media_category. First I tried this with the post-endpoint, this has worked well, but when I try the same with the media-endpoint it does not work.

Is the object type for the media-endpoint anything else than media?

My current code:

<?php
/**
 * Plugin Name: REST Response Modifier
 * Description: A simple plugin to modify the rest api
 * Author: TheBalco
 * Author URI: http://somepage.dev
 */

add_action('rest_api_init', 'tb_add_custom_rest_fields');

function tb_add_custom_rest_fields() {
    // schema
    $media_category_schema = array(
        'description'   => 'Categories of the media item',
        'type'          => 'string',
        'context'       => ['view']
    );

    // registering the field
    register_rest_field(
        'media',
        'media_category',
        [
            'get_callback'      => 'get_media_category',
            'update_callback'   => null,
            'schema'            => $media_category_schema
        ]
    );
}

/**
 * Callback
 * @param  array            $object         The current post object
 * @param  string           $field_name     The name of the field
 * @param  WP_REST_request  $request        The current request
 * @return string                           The return value
 */
function get_media_category($object, $field_name, $request) {
    return 'this-is-a-test';
    //return get_the_author_meta( 'display_name', $object['author'] );
}

If I replace the media in register_rest_field with post, it works for the post-endpoint. But it doesn't work for the media-endpoint.

Anybody got a solution for this?

Answer 1

I found the solution for my problem. The object type for media is not media, it's just attachment. So the following code works for me:

<?php
/**
 * Plugin Name: REST Response Modifier
 * Description: A simple plugin to modify the rest api
 * Author: TheBalco
 * Author URI: http://somepage.dev
 */

add_action('rest_api_init', 'tb_add_custom_rest_fields');

function tb_add_custom_rest_fields() {
    // schema
    $media_category_schema = array(
        'description'   => 'Categories of the media item',
        'type'          => 'string',
        'context'       => ['view']
    );

    // registering the field
    register_rest_field(
        'attachment',
        'media_category',
        [
            'get_callback'      => 'get_media_category',
            'update_callback'   => null,
            'schema'            => $media_category_schema
        ]
    );
}

/**
 * Callback
 * @param  array            $object         The current post object
 * @param  string           $field_name     The name of the field
 * @param  WP_REST_request  $request        The current request
 * @return string                           The return value
 */
function get_media_category($object, $field_name, $request) {
    return 'this-is-a-test';
    //return get_the_author_meta( 'display_name', $object['author'] );
}