What exactly does presentModalViewController do?

If I have a navigationController which is init with a root view controller MyViewController's instance.

And in that MyViewController's code I can use

AnotherViewController *vc = [[AnotherViewController alloc] init];
[self presentModalViewController:vc animated:YES];

or

AnotherViewController *vc = [[AnotherViewController alloc] init];
[self.navigationController presentModalViewController:vc animated:YES];

I found these two works the same. Both present th开发者_运维问答e modal view correctly.And I have found that the presented AnotherViewController's "parentViewController" property are all set to the navigation controller.

Why would this happen?the presentModalViewController automatically detect that the self is the subview of the navigation controller and re send the message to navigation controller?

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Because MyViewController is the root view controller of the UINavigationController, it gets the convenience method of presentModalViewController: animated: by default. So when you say self.navigationController, it is referring to the same navigationController that presentModalViewController gives you. I think Apple is just trying to make it more intuitive to use the convenience method.