When I have to use a scrollView, I prefer put another scrollView inside the main view of viewController, even the scrollView is the only view in the main view of viewController. And I strongly suggests others use it this way other than make main view of viewController a scrollView. This approach is scalable.
What I was trying to solve is that when I show this scrollView viewController from a navigationController, the navigation bar overlaps some content of my scrollView.
I figured out there are two ways to do such things:
Adjust Scroll View Insets property to false and set scrollView's Y constraints as these two: scrollView.top = TopLayoutGuide.bottom
scrollView.bottom = BottomLayoutGuide.top
Adjust Scroll View Insets property to true and set scrollView's Y constraints as these two: scrollView.top = superview.top
scrollView.bottom = BottomLayoutGuide.top