title: Multiple Documents in a Single Window in Cocoa
body: <p>I want to write an application which may have multiple documents in a single window via a tabbed interface.  Should I avoid the NSDocument architecture (the Cocoa Document-based Application template)?  As far as I can tell, it supports only one or more window per document but not vice versa.</p>
  
  <p>I have been wrestling with this question for a while and have already built much of my application on the NSDocument architecture but I cannot figure out a good way to associate multiple documents with a single window.</p>
  
  <p>EDIT: I want to have project document windows in addition to basic document windows.  At this level of complexity, would it still be worth hacking the NSDocument architecture?  Did Apple write Xcode (which works this way) using the NSDocument architecture?</p>