jQuery UI dialog - check if exists by instance method

I'd like to use instance method for testing if jQuery UI Dialog widget has been initialized or not. Regarding to API, this is possible, but it doesn't work for me:

Uncaught Error: cannot call methods on dialog prior to initialization; attempted to call method 'instance'

demo: http://jsfiddle.net/mDbV7/

UPDATE:

This was a mistake in the documentation, instance method will be available from version 1.11.0, see this issue.

The latest version of jQuery UI no longer allows you to call UI methods on items that are not initialized yet. I've just been wrapping them in an if statement, like:

if ($("#divToBeDialoged").hasClass('ui-dialog-content')) {
    // do whatever
} else {
    // it is not initialized yet
}

Edit: changed class name, thanks @dmnc

It is also a good habit to empty and destroy dialogs once you're done using them. I usually use this code in the close event of each dialog

$("#myDialog").dialog({
    // other options
    close: function(event, ui) {
        $(this).empty().dialog('destroy');
    }
}

That'd be my advice, rather than asking every time if a dialog exists in an instance make sure that each dialog cleans up after itself.

You can use:

if($('#id').is(':ui-dialog')) {
}

or

    var obj = $('<div>test</div>').dialog();
    if (obj.is(':ui-dialog')) {
      alert('I\'m a dialog')
    }

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<link rel="stylesheet" href="https://ajax.googleapis.com/ajax/libs/jqueryui/1.11.4/themes/smoothness/jquery-ui.css">
<script src="https://ajax.googleapis.com/ajax/libs/jqueryui/1.11.4/jquery-ui.min.js"></script>

If you are making that dialog from an existing id in your html code, like this example:

$('#main').dialog({});

Notice that dialog() adds the class ui-dialog in a <div> parent element generated for it to work. At the #main element, the classes added by dialog() are: ui-dialog-content and ui-widget-content (in jquery-ui-1.9.2). So, in this case, following the example from @jbabey, you can check the existing dialog doing:

if ($('#main').hasClass('ui-dialog-content')) {
    // do whatever
}

     if ($('#update').is(':data(dialog)')) 
     {
              //#update has dialog
     }
     else
     {
              //#update does't have dialog
     }