class MessageCommand in Drupal 8

AJAX command for a JavaScript Drupal.message() call.

Developers should be extra careful if this command and \Drupal\Core\Ajax\AnnounceCommand are included in the same response. Unless the `announce` option is set to an empty string (''), this command will result in the message being announced to screen readers. When combined with AnnounceCommand, this may result in unexpected behavior. Manual testing with a screen reader is strongly recommended.

Here are examples of how to suppress announcements:

$command = new MessageCommand("I won't be announced", NULL, [
  'announce' => '',
]);

Hierarchy

• class \Drupal\Core\Ajax\MessageCommand implements CommandInterface, CommandWithAttachedAssetsInterface

See also

\Drupal\Core\Ajax\AnnounceCommand

Related topics

Ajax API

Overview for Drupal's Ajax API.

1 file declares its use of MessageCommand

AjaxTestMessageCommandForm.php in core/modules/system/tests/modules/ajax_test/src/Form/AjaxTestMessageCommandForm.php

File

core/lib/Drupal/Core/Ajax/MessageCommand.php, line 28

Namespace

Drupal\Core\Ajax

class MessageCommand implements CommandInterface, CommandWithAttachedAssetsInterface {

  /**
   * The message text.
   *
   * @var string
   */
  protected $message;

  /**
   * Whether to clear previous messages.
   *
   * @var bool
   */
  protected $clearPrevious;

  /**
   * The query selector for the element the message will appear in.
   *
   * @var string
   */
  protected $wrapperQuerySelector;

  /**
   * The options passed to Drupal.message().add().
   *
   * @var array
   */
  protected $options;

  /**
   * Constructs a MessageCommand object.
   *
   * @param string $message
   *   The text of the message.
   * @param string|null $wrapper_query_selector
   *   The query selector of the element to display messages in when they
   *   should be displayed somewhere other than the default.
   *   @see Drupal.Message.defaultWrapper()
   * @param array $options
   *   The options passed to Drupal.message().add().
   * @param bool $clear_previous
   *   If TRUE, previous messages will be cleared first.
   */
  public function __construct($message, $wrapper_query_selector = NULL, array $options = [], $clear_previous = TRUE) {
    $this->message = $message;
    $this->wrapperQuerySelector = $wrapper_query_selector;
    $this->options = $options;
    $this->clearPrevious = $clear_previous;
  }

  /**
   * {@inheritdoc}
   */
  public function render() {
    return [
      'command' => 'message',
      'message' => $this->message,
      'messageWrapperQuerySelector' => $this->wrapperQuerySelector,
      'messageOptions' => $this->options,
      'clearPrevious' => $this->clearPrevious,
    ];
  }

  /**
   * {@inheritdoc}
   */
  public function getAttachedAssets() {
    $assets = new AttachedAssets();
    $assets
      ->setLibraries([
      'core/drupal.message',
    ]);
    return $assets;
  }

}

Members

Name	Modifiers	Type	Description	Overrides
MessageCommand::$clearPrevious	protected	property	Whether to clear previous messages.
MessageCommand::$message	protected	property	The message text.
MessageCommand::$options	protected	property	The options passed to Drupal.message().add().
MessageCommand::$wrapperQuerySelector	protected	property	The query selector for the element the message will appear in.
MessageCommand::getAttachedAssets	public	function	Gets the attached assets. Overrides CommandWithAttachedAssetsInterface::getAttachedAssets
MessageCommand::render	public	function	Return an array to be run through json_encode and sent to the client. Overrides CommandInterface::render
MessageCommand::__construct	public	function	Constructs a MessageCommand object.