Question

I am new to iOS programming. I see that there are functions defined in my view controller such as

- (void) viewDidLoad

How is viewDidLoad an instance method as denoted by the hyphen? I don’t think I ever instantiate this class.

Answer 1

When you create a *.xib file (the view) in Xcode and set its class (the controller) in the identity inspector, an instance of that class is instantiated when you load the *.xib file via

[MyViewController alloc] initWithNibName:@"MyViewController" bundle:nil]

And viewDidLoad is called automatically once the *.xib file has fully loaded.

You can see this by simply creating a new Single View iOS project in Xcode. In AppDelegate.m you’ll see a line similar to the one above in the -(BOOL) application: didFinishLaunchingWithOptions: method. In the ViewController.xib file, if you click on “File’s Owner” and show the Identity Inspector, you’ll see that the class ViewController is the one “linked” with the *.xib.