Multiple Documents in a Single Window in Cocoa

I have the same kind of project — different independent documents that I want to present in a single window, with a sidebar that allows switching between documents — so I have done a little bit of searching myself.

I just found an interesting lead by reading Cocoadev's Document Based App With One Window For All Documents reference. It appears, from MikeTrent's answer, that using NSDocument is a very viable way to go. You just need subclassing NSDocumentController.

I also like Abhi's idea to use a borderless child window.

Using an NSDocument-based architecture isn't necessarily a bad idea in this case; but it might require quite a bit of haquery.

It is quite likely that you will have to not only subclass NSDocument, but also it's more rarely subclassed sibling NSDocumentController. Once this is done, it should be a simple matter to hijack and avoid calls to -makeWindowControllers and other window-related methods, allowing you to wrap the document "windows" in whatever fashion you please, but still retain the benefits of the document-based application.

I tried shoehorning an NSDocument app into a single window tabbed interface a few years ago, and ended up so frustrated after a few months I went back and refactored out the document architecture pieces. It's not impossible, but you end up working around so many problems that the final result barely resembles a proper NSDocument app. It's better to just rewrite the bits you do need, than end up with a lot of code just to subvert the Cocoa frameworks.