Re: How to enforce a single NSDocument ... or should I do something else?
Re: How to enforce a single NSDocument ... or should I do something else?
- Subject: Re: How to enforce a single NSDocument ... or should I do something else?
- From: Martin Stanley <email@hidden>
- Date: Tue, 5 Jan 2010 12:34:38 -0500
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
>>
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