[viewController.view removeFromSuperView]之间的区别;和[uiviewController removeFromParentViewController];？

Question

之间有什么区别

[viewController.view removeFromSuperView]; 

和

[viewController removeFromParentViewController]; ?

我只想从UIScrollView中删除子视图，当然代码应该是这样的[viewController.view removeFromSuperView];

但是当我尝试[viewController removeFromParentViewController];时，它似乎也很有用。怪异！