我知道有三种方法可以改变 iOS 中的视图
1.
[self addChildViewController:thirdViewController];
[contentView addSubview:thirdViewController.view];
2.
First * sVC = [[First alloc] initWithNibName:@"First" bundle:[NSBundle mainBundle]];
[self presentModalViewController:sVC animated:YES];
3.
MyViewController *sampleViewController = [[[MyViewController alloc]initWithXXX] autorelease];
[self.navigationController pushViewController: sampleViewController animated:true];
pushViewController 需要导航控制器,我理解。但是,何时使用 addChildViewController 和 presentModalViewController?