Question

I’m building a Cocoa application and have a question about using window controllers. The idea is that if the user selects New from the menu bar, an instance of MyWindowController which is a subclass of NSWindowController is created and a new window from MyWindow.xib is displayed.

I’m handling the action in the application delegate. From what I have seen after searching around something like the following could be done. Once the window is displayed I don’t have any reason to store a pointer to the window controller anymore and since I allocated it I also autorelease it before displaying the window.

[[[[MyWindowController alloc] init] autorelease] showWindow:self];

Since the window is released soon afterwards the window will briefly display on the screen and then go away. I have found a solution where I retain the window controller in the -showWindow: method and let it release itself once it gets a windowWillClose notification.

- (IBAction)showWindow:(id)sender
{
    [self retain];
    [[NSNotificationCenter defaultCenter] addObserverForName:NSWindowWillCloseNotification
                                                      object:self.window
                                                       queue:nil
                                                  usingBlock:^(NSNotification *note) {
                                                      [self release];
                                                  }];
    [super showWindow:sender];
}

Is there a better way to do this? I have searched the Apple documentation and have not found anything on which practices to use. It sounds like something very basic which it should cover so maybe I’m just searching with the wrong terms.

Answer 1

Normally you would hold on to the window controller, and only release it when you are done with it. I’d say that your app delegate would be responsible for that. Just store them in an array if there can be multiple. Whilst your solution may work, it’s not very elegant.

If you are working on a document based Cocoa app, you create the window controller in your document subclass method makeWindowControllers and let that class hold a pointer to your window controller.