/**
* Add an attachment to the message.
*
* @param mixed $attachment
* @return $this
*/
public function attach($attachment)
{
if ($attachment instanceof Attachment) {
$this->attachments[] = $attachment;
return $this;
} elseif (is_array($attachment)) {
$attachmentObject = new Attachment($attachment);
if (!isset($attachment['mrkdwn_in'])) {
$attachmentObject->setMarkdownFields($this->getMarkdownInAttachments());
}
$this->attachments[] = $attachmentObject;
return $this;
}
throw new InvalidArgumentException('Attachment must be an instance of Maknz\\Slack\\Attachment or a keyed array');
}