Thanks for the very quick response! I don't quite understand step 2: how do I decide what to return from -openDocumentWithContentsOfURL: if the callback hasn't been called yet and therefore I don't know if the user cancelled the close of the first document?
I think the basic problem for me is that -canCloseDocument… does not block. Martin On 2010-01-05, at 12:10 PM, Mike Abdullah wrote: > Override -openDocumentWithContentsOfURL: > > 1. If you've already got a document open, send -canCloseDocument… to the open > document, supplying the callback info > > 2. Either: > A) Return nil and an NSUserCancelled error. > B) Return the existing document. > > 3. When you get the callback from -canCloseDocument… call super's > implementation of -openDocumentWithContentsOfURL: > > On 5 Jan 2010, at 16:45, Martin Stanley wrote: > >> I have a Core-Date application that uses the Cocoa Document architecture >> (NSPersistentDocument) and would like to ensure that the user only can have >> 1 document open at a time. Think of this application as similar to Mail.app >> or Addressbook.app, etc. except that I would like the user to be able to >> open different persistent stores at will, just not simultaneously. >> >> (As an aside, the reason for this is because my document has many related >> windows and I think it would be confusing for the user. It would not be >> obvious which auxiliary window relates to which document. I may fix this in >> the future by using the concept of Inspectors, but at this point I'm not >> sure if this is the correct model.) >> >> I searched extensively and came up with the recommendation that I subclass >> NSDocumentController and override: >> - (id)openDocumentWithContentsOfURL:display:error: >> This was recommended over simply trapping the open menu item(s). >> >> >> This seemed very promising until I ran into a stumbling block. In >> openDocumentWithContentsOfURL:display:error: I check to see if there is an >> already open document and if so call: >> canCloseDocumentWithDelegate:shouldCloseSelector:contextInfo: >> with an appropriate delegate and selector. The problem is that this returns >> immediately, even in the case when the document is dirty and it presents a >> modal dialog to the user. Because of this, the 2nd document is opened before >> I have a chance to deal with the first one. >> >> All of this is making me wonder if I'm taking the wrong approach. >> >> Should I figure out a way to prevent the 2nd document from opening before >> the first one is either saved or abandoned: (override >> canCloseDocumentWithDelegate:shouldCloseSelector:contextInfo: in my >> NSPersistentDocument subclass)? This feels like the solution is getting >> uglier by the minute. >> >> Or is there a much easier way to accomplish what I want to do? Or should I >> be looking at a entirely different approach for my application? >> >> Thanks, >> Martin >> >> _______________________________________________ >> >> Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) >> >> Please do not post admin requests or moderator comments to the list. >> Contact the moderators at cocoa-dev-admins(at)lists.apple.com >> >> Help/Unsubscribe/Update your Subscription: >> http://lists.apple.com/mailman/options/cocoa-dev/cocoadev%40mikeabdullah.net >> >> This email sent to cocoa...@mikeabdullah.net > _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
