Objective-c – UIViewController subclass init not called when loading from nib

interface-buildermodel-view-controllernibobjective cuikit

I tried overriding the default initWithNibName designated initializer of a UIViewController subclass like so:

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
    if (self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]) {
        // Custom initialization
    }
    return self;
}

I have also included its definition in the header file. However, when my Application Delegate nib loads the viewcontroller, the initializer is not invoked, only -viewDidLoad.

How does the nib magic instantiate my view controller then? Why do all the XCode templates state

// The designated initializer. Override if you create the controller programmatically and want to perform customization that is not appropriate for viewDidLoad.

Is it correct my initWithNibName isn't called when the viewcontroller is loaded form another nib?

Best Answer

You need to put your initialization code inside the awakeFromNib method for it to be run when loaded from Nib. The Nib file contains an archived version of the objects that it contains, so in principle, they do not need to be initialized again.

Related Solutions

Objective-c – Order of UIViewController initialization and loading

The view loading system on the iPhone works like this:

When you initialize a view controller (either with -init or -initWithNibName:bundle:), it doesn't actually create and initialize the view. When you call -view for the first time, it calls -loadView. By default, -loadView just loads the view from the xib file (nibName). If you override this, though, you're responsible for creating the view and assigning it to the view controller's view property. As an example:

- (void)loadView
{
   UIView *view = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];
   // add subviews 
   self.view = view;
   [view release];
}

Every time you create the view, which is different from the view becoming visible and showing onscreen, it calls -viewDidLoad. (-viewDidAppear/-viewDidDisappear is for the visibility of the view on-screen)

Since we're already off-track, let's consider memory management. When the view is offscreen, the system will automatically set the view property of a view controller to nil. The problem is that all the subviews of that view are leaking. How so? Well, the retain count for each subview is 2 (views retain subviews, and your view controller has an outlet/ivar to it). When the view is nil, the retain count of that view is 1. It doesn't make sense for a view to stick around if a view isn't showing, so you set it to nil in -viewDidUnload (which is a hook for whenever the view is set to nil).

Ios – Loaded nib but the ‘view’ outlet was not set

Here's what worked for me:

Open the XIB file causing problems
Click on file's owner icon on the left bar (top one, looks like a yellow outlined box)
If you don't see the right-hand sidebar, click on the third icon above "view" in your toolbar. This will show the right-hand sidebar
In the right-hand sidebar, click on the fourth tab--the one that looks a bit like a newspaper
Under "Custom Class" at the top, make sure Class is the name of the ViewController that should correspond to this view. If not, enter it
In the right-hand sidebar, click on the last tab--the one that looks like a circle with an arrow in it
You should see "outlets" with "view" under it. Drag the circle next to it over to the "view" icon on the left bar (bottom one, looks like a white square with a thick gray outline
Save the xib and re-run

Best Answer

Related Solutions

Objective-c – Order of UIViewController initialization and loading

Ios – Loaded nib but the ‘view’ outlet was not set

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