How do I auto size a UIScrollView to fit its content

The best method I've ever come across to update the content size of a UIScrollView based on its contained subviews:

Objective-C

CGRect contentRect = CGRectZero;

for (UIView *view in self.scrollView.subviews) {
    contentRect = CGRectUnion(contentRect, view.frame);
}
self.scrollView.contentSize = contentRect.size;

Swift

let contentRect: CGRect = scrollView.subviews.reduce(into: .zero) { rect, view in
    rect = rect.union(view.frame)
}
scrollView.contentSize = contentRect.size

UIScrollView doesn't know the height of its content automatically. You must calculate the height and width for yourself

Do it with something like

CGFloat scrollViewHeight = 0.0f;
for (UIView* view in scrollView.subviews)
{
   scrollViewHeight += view.frame.size.height;
}

[scrollView setContentSize:(CGSizeMake(320, scrollViewHeight))];

But this only work if the views are one below the other. If you have a view next to each other you only have to add the height of one if you don't want to set the content of the scroller larger than it really is.