Question

I ask this question because it appears that viewDidLoad gets called before the main block of the initializer does and the class variables I’m initializing in the initializer are turning up nil in viewDidLoad. For your reference, I’m doing this entire viewcontroller programmatically and I’ve created a custom initializer so I can take in various parameters to be used in my viewcontroller. My custom initializer calls UIViewControllers designated initializer of course.

Basically, I’m curious about what is the proper design pattern for sending in parameters to a UIViewController? I’ve read other threads about this and haven’t really gotten a definitive answer. Should I just skip the initializer and set the properties manually (from outside the class)? That seems kind of bleh, I’d really like to send in some parameters and am curious how others go about doing this?

Answer 1

The reason viewDidLoad is called before initialization completes, is probably because you call the view method in the initializer. For example:

- (id)init
{
    if ((self = [super init])) {
        _thing = 123;
        _other = self.view.frame.size.width / 2;
    }

    return self;
}

viewDidLoad is called when the view loads. And the view loads as soon as you call the view method (or access the view property, if you prefer). So you should avoid referencing the view in init.

To answer your question, I prefer to create an init method for my view controllers.

- (id)initWithThing:(MyThing *)thing thang:(MyThang *)thang
{
    if ((self = [super init])) {
        _thing = [thing retain];
        _thang = [thang retain];
        // ...
    }

    return self;
}

You can also use properties to set extra variables after initing. Personally I prefer to do this with optional properties only, though, and put required properties in the init method. That way I can’t init the view controller with an invalid state.