Question

I have a UIViewController called LaunchController that is launched in my iPhone app when the app first opens:

@interface LaunchController : UIViewController<UINavigationControllerDelegate, UIImagePickerControllerDelegate>

Then, when a button is clicked, I push another view controller:

 MainController *c = [[MainController alloc] initWithImage:image];
 [self presentModalViewController:c animated:NO];

MainController has the following constructor, which I use:

- (id)initWithImage:(UIImage *)img
{
    self = [super init];
    if (self) {
        image = img;
        NSLog(@"inited the image");
    }

    return self;
}

and then it has a viewDidLoad method as follows:

- (void)viewDidLoad
{
    NSLog(@"calling view did load");
    [super viewDidLoad];

    UIImageView *imageView = [[UIImageView alloc] initWithImage:image];
    [self.view addSubview:imageView];
    NSLog(@"displaying main controller");
}

When the program runs, I see that the constructor for MainController is called (due to the output of NSLog), however viewDidLoad never gets called, even though I am calling presentModalViewController. Why is this? Why isn’t viewDidLoad being called?

Answer 1

I think it is something as followings. When you need the property of view inside UIViewController, it will be loaded with lazy manner.

- (UIView *)view 
{
   if (_view == nil) {
      [self loadView]; //< or, the view is loaded from xib, or something else.
      [self viewDidLoad];
   }

   return _view;
} 

After the view initialized, it will call viewDidLoad to inform the UIViewController.