我知道在iOS中有三种改变视图的方式。
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,这点我理解。但是什么时候使用addChildViewController和presentModalViewController呢?