On 21-Oct-09, at 12:57 AM, Graham Cox wrote:
On 21/10/2009, at 3:43 PM, Ben Haller wrote:
There must be a good, clean way to do this. Anyone?
Well, the expected way is to have different types for your
documents. You can still map them all to the same class, and
discriminate in the -initWithType:error: method to set up the
appropriate model.
However, if you really can't or don't want to do that, I think what
you've done is right. Because you have a special designated
initializer, you have no option but to manually make the controllers
and add the document to the controller.
OK, I've switched over to an NSDocumentController and using
different types for my different models. That turned out to be a
forced move, because NSApplication's delegate method -
applicationOpenUntitledFile: does not get called when the user chooses
New from the File menu; that seems to go right to
NSDocumentController. -applicationOpenUntitledFile: only seems to get
called for the new document created when an app is launched or brought
front without an open document. I could have started changing the
actions for menu items and so forth, but I decided that since my app
is document-based, I ought to go with the document architecture. So I
now have an NSDocumentController subclass, and I override
openUntitledDocumentAndDisplay:error:. That seems to be in the code
path for all kinds of new documents.
However, I still find this architecture quite unsatisfying. My -
openUntitledDocumentAndDisplay:error: subclass still needs to do way
too much work:
- (id)openUntitledDocumentAndDisplay:(BOOL)displayDocument error:
(NSError **)outError
{
NSString *chosenModelName = [AKNewModelController runNewModelPanel];
if (chosenModelName)
{
NSError *error = nil;
AKDocument *document = [self
makeUntitledDocumentOfType:chosenModelName error:&error];
if (error)
{
if (outError)
*outError = error;
return nil;
}
[self addDocument:document];
if (displayDocument)
{
[document makeWindowControllers];
[document showWindows];
}
return document;
}
return nil;
}
The sequence of -makeUntitledDocumentOfType:error:, then
makeWindowControllers, then showWindows, is already in super, but I
don't have any way to make super do it. So I have to duplicate that
sequence in my own code, which makes my code vulnerable to
architectural changes in NSDocument. I gather this sequence has
already changed at least once in the past, so it is clearly fragile.
There really must be a better way to do this; I feel like I'm
running at counter purposes to the design of the framework. Anyone
have any better suggestions?
I'm curious as to why -makeUntitledDocumentOfType:error: doesn't do
the work of adding the document, setting up its windowController,s and
showing the windows. That would seem like the natural design to me,
rather than making everyone that calls that method do that work
themselves. Is there a reason for this design?
Ben Haller
Stick Software
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