Do we really need "UIViewController"?

I studied the "Scratch Off Effect" code from http://buildingmyworld.wordpress.com/ and found a very interesting thing.

There's only a "main.h", an "AppDelegate", 2 "UIView" and - - - an "UIViewController" which is not been used at all. If you look at the blog, the author also mentioned "btw: there is a view controller called ScratchTiceketViewController. Just ignore it. It was my test view controller and I’m to lazy to remove it )"

So I inserted a few NSLog in each of the methods to show how/when each method been called, and removed that "ScratchTicketViewController" completely. The code still works! What the....

This is totally different from what I learned so far - so we can have a application that has no UIViewController at all, very interesting!

Next, I tried to add an UIView and an UIViewController to the project and compare the differences.

For UIView, as below it only has 3 methods, and one of them - "drawRect" disabled -- I remember seeing that name in previous Quartz 2D test project. I guess if you need any other methods, can still be triggered from the "initWithFrame" method.

@implementation UIView1

- (id)initWithFrame:(CGRect)frame

{

    self = [super initWithFrame:frame];

    if (self) {

        // Initialization code

    }

    return self;

}

/*

// Only override drawRect: if you perform custom drawing.

// An empty implementation adversely affects performance during animation.

- (void)drawRect:(CGRect)rect

{

    // Drawing code

}

*/

- (void)dealloc

{

    [super dealloc];

}

@end

However, for UIViewController it's a lot more complicate. As below there are a few extra ones: "loadView", "viewDidLoad", "viewDidUnload", "didReceiveMemoryWarning" and "shouldAutorotateToInterfaceOrientation". Which is definitely more complicate and powerful than the simple UIView above.

@implementation UIViewController1

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil

{

    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];

    if (self) {

        // Custom initialization

    }

    return self;

}

- (void)dealloc

{

    [super dealloc];

}

- (void)didReceiveMemoryWarning

{

    // Releases the view if it doesn't have a superview.

    [super didReceiveMemoryWarning];

    

    // Release any cached data, images, etc that aren't in use.

}

#pragma mark - View lifecycle

/*

// Implement loadView to create a view hierarchy programmatically, without using a nib.

- (void)loadView

{

}

*/

/*

// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.

- (void)viewDidLoad

{

    [super viewDidLoad];

}

*/

- (void)viewDidUnload

{

    [super viewDidUnload];

    // Release any retained subviews of the main view.

    // e.g. self.myOutlet = nil;

}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation

{

    // Return YES for supported orientations

    return (interfaceOrientation == UIInterfaceOrientationPortrait);

}

@end

I guess it all depends on the purpose of the code, if it's just a simple test project/application, which you don't care whether there's orientation change or memory warning or use NIB files, a simple UIView should be sufficient. For a more "normal", "fully functioning" project/application which is to be submitted to App Store, you would definitely still have to use UIViewController.

Ah! Feels good to learn new things everyday!

Posted in: Question