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I have a problem when reloading views. OSX is not as simple as IOS.

In MainMenu.xib I have an NSBox. As per Hillegrath, several views are stored in an array and when a segmented button is pressed the views are exposed. This works properly. My frustration involves revisiting these views when changes have been made that should cause them to redisplay new values through [self someAction]. Actions in two of the views alter (global)values that should propagate changes in the other views. I am using a window controller w/xib (MainMenu) to hold the box which contains the views. I also title the views in code.

The global ivar values change properly when required and the log shows that. However dependent operations do not occur when the view are revisited, ie, update view specifics.

What appears to happen is that loadView is not called when the various views are displayed, ** **. awakeFromNib and loadView operate correctly when each view is first displayed but not ever on redisplays. This implies that that the view may be hidden but viewDidUnhide has no effect.

The view changing code (from an SO MVC answer and Hillegrath) is

 NSViewController *activeVC =
        (NSViewController *) self.viewControllers[index];
   // [_box setContentView:nil];
    [_box setContentView:activeVC.view];
    [_box setNeedsDisplay:YES];

From the copied code it can be seen that I have also attempted setting the active content to nil before setting a new view but, to no avail.

Any ideas, recommendations, notifications fail to work either but may not set up correctly.

Thanks

Michael Way
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1 Answers1

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It looks like you’re confusing view loading with display. -awakeFromNib is received by a nib file object only when the nib file is loaded. Similarly, -loadView is received by the view controller only when its corresponding nib file is loaded. Since you are keeping your view controllers in an array, those view controllers do not get deallocated, hence their corresponding nib files are never unloaded whilst the array is alive. This is reasonable behaviour, but you must bear in mind that -awakeFromNib and -loadView are only executed once in this case because nib loading is executed only once.

Since it seems that you are manually populating the view in -loadView, you’ll also have to do that whenever you set that view as the box’s content view (assuming you’re not always updating the view whenever the model changes). For instance, you could have a -reloadData method in your view controller and both -loadView and your box’s content view swapping method would use -reloadData.

Alternatively, you could set your model object as the represented object of your view controller and bind the controls in the corresponding view to properties of that represented object. NSViewController exposes a representedObject property that’s convenient for bindings.

For the record, -[NSBox setContentView:] marks the box for redisplay, so you don’t need to send it -setNeedsDisplay:YES.

(and make sure _box actually points to the NSBox instance)

  • Thanks for your reply. However, one of my attempts has been to use -loadView to call a method to update the controls. Since -loadView is only called on initial load and not subsequent display, no joy. I will continue to experiment. – Michael Way Jun 06 '13 at 18:43
  • @MichaelWay The point of my answer is that you must call a method to update the controls _whenever you replace the content view_ (or whenever you update your model) since `-loadView` is not enough. –  Jun 07 '13 at 04:14
  • Turned out to be a simple fix. In the NSWindowController, showPane method, I send a notification. In each viewController, when notified, call viewIsVisible: which calls the required updating methods. Now I can carry on. As a matter of fact, the updating methods were the ones that could not be called previously – Michael Way Jun 07 '13 at 05:44