private function register_fields_for_certificates() {

		foreach ( $this->get_fields_for_certificates() as $key => $schema ) {

			$schema['context'] = array( 'view', 'edit' );

			register_rest_field(
				array( 'llms_certificate', 'llms_my_certificate' ),
				"certificate_{$key}",
				array(
					'schema'          => $schema,
					'get_callback'    => function( $object ) use ( $key ) {
						$cert = llms_get_certificate( $object['id'], true );
						$func = "get_{$key}";
						return $cert ? $cert->$func() : null;
					},
					'update_callback' => function( $value, $post ) use ( $key ) {
						$cert = llms_get_certificate( $post->ID, true );
						return $cert ? $cert->set( $key, $value ) : null;
					},
				)
			);

		}

	}