Appcelerator. Open modal window in single context

I am developing an iOS app with Appcelerator Titanium Studio and SDK 1.7.2. I am working in a single context way of doing things (like tweetanium). I know how to switch between windows but how can I open a modal window?

This k开发者_运维知识库ind of works but I cannot add a button to the navBar. It also does not feel right at all.

 var wind = UI.Win({

  title: 'Twitter',
  modal: true

 });

 wind.open(Window.ShareTwitter());

Thankful for all input!

you open a modal window the way you always do, nothing has changed...

window.open({modal:true});