Add ACF fields to WP JSON API V2

acf_api.php

<?php

function d7_add_acf_to_json_api_v2($object, $field_name, $request){
	if ( function_exists('get_fields') ) {
		return get_fields($object['id']);
	}
}

if ( is_plugin_active('rest-api/plugin.php') ) {
	add_filter('rest_api_init', function(){

		// Get all post types
		$types = get_post_types(array('_builtin' => false), 'objects');

		// Find post types that are in the api
		foreach ( $types as $slug => $type ) {
			if ( isset($type->show_in_rest) && $type->show_in_rest ) {

				// Register the type's ACF fields
				register_api_field($slug, 'custom_fields', array(
					'get_callback' => 'd7_add_acf_to_json_api_v2',
					'update_callback' => null,
					'schema' => null
				));

			}
		}
	});
}