What method is called first when storyboard loads?

Question

Using Xcode 4.2, in my application, a view loading is triggered by a segue event. What method will be called first inside a view controller?

-(void) viewWillAppear:(BOOL)animated works, but is it the first?

Initialization happens from the Storyboard it seems, init method is never manually called, upon object creation.

Let me clarify, when creating an instance of a class manually, we usually [[alloc]init] it first. [init] in this case, is the first method to be executed and a good place for various initializations.

What is the equivalent of init method when class instantiation happens via a segue event? In such a case, what method should contain all initialization logic?

Solution 1

I think the best option is -(void)awakeFromNib. This only occurs the once, whereas viewWillAppear and viewDidLoad etc could be called more than once after your initialisation.

UPDATE: As pointed out by Jean-Denis Muys below, -(id)initWithCoder:(NSCoder *)decoder is a better option for an initialiser that only gets called once as -(void)awakeFromNib has the potential to be called more than once.

Solution 2

According to Apple's View Controller Programming Guide,

When you create a view controller in a storyboard, the attributes you configure in Interface Builder are serialized in an archive. Later, when the view controller is instantiated, this archive is loaded into memory and processed. The result is a set of objects whose attributes match those you set in Interface Builder. The archive is loaded by calling the view controller’s initWithCoder: method. Then, the awakeFromNib method is called on any object that implements that method. You use this method to perform any configuration steps that require other objects to already be instantiated.

Solution 3

I would advise not to use awakeFromNib. I use simply both of these functions

- (id)initWithFrame:(CGRect)frame {
    if (self = [super initWithFrame:frame]) {
        [self setup];
    }
    return self;
}

- (id)initWithCoder:(NSCoder *)aDecoder {
    if (self = [super initWithCoder:aDecoder]) {
        [self setup];
    }
    return self;
}

- (void)setupButton {
    /* get ready to be called twice */
    self.layer.cornerRadious = 10.0f;
}

because: let's say you subclassed UIButton. You must be ready for two scenario:

scenario 1. If you add the button programmatically --> initWithFrame->setupUI will be called scenario 2. If you add the button using NIb --> initWithCoder->setupUI will be called.

Comments

[DZenBot]

-(void)awakeFromNib never gets called when loading controller with segue. Does anybody have a better answer?

[DonnaLea]

@DZenBot I think you're mistaken. I just double checked and -(void)awakeFromNib is being called on my UIViewController which is loaded with a segue.

[Jean-Denis Muys]

except that -(void)awakeFromNib can be called several times (in some rather uncommon cases). The initializer that is called only once is initFromCoder

[DZenBot]

Yes, I have tested -(void)initFromCoder method, and it gets called all the time with no exception. -(void)awakeFromNib never got called when I perform a segue load. Odd isn't it?

[DonnaLea]

I was not aware that -(void)awakeFromNib could be called multiple times. I guess that makes sense in the situation for when viewDidLoad gets called a second time. I've since started using initFromCoder as per your suggestion and that has been working like a charm too. I'll update my answer.