Better way to tell if widget already rendered?

Better way to tell if widget already rendered?


Seems like this is an easy one, but I'm not having luck.
Currently I do this.
if( ! $("#widget-id").hasClass("ui-dialog-content") ) {
// setup dialog and do other expensive stuff
}
But of course that depends on the CSS class names used. Is there a
better way, using only the public API?
Thanks.