Multiple Documents in a Single Window in Cocoa

Question

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.

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.

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?

Answer 1

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.

Answer 2

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.

Answer 3

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.

Answer 4

Another technique, which I haven't tried yet but plan to, is to have a borderless window for each document. This way one document has one window, which may or may not be visible.

Then, have a wrapper window containing the actual window border, and any controls to switch between which borderless document window/windows are visible. The document window is a child window of the wrapper, which ensures both will be linked when a window is moved/minimised/closed/etc.

For each borderless document window, the wrapper window has a placeholder view that, when resized, will resize the document window, and also inject the document window's view into the responder chain (any event sent to the placeholder view, will be sent to the document window's view before being passed on to the placeholder's parent view).

There are still some minor details to work out, but I think this approach will work well.