UIScrollView with scaled UIImageView using autolayout

Question

Consider a UIScrollView with a single subview. The subview is an

Answer 1

In my case it was a full width UIImageView the had a defined height constraint that causing the problem.

I set another constraint on the UIImageView for the width that matched the width of the UIScrollView as it is in interface builder then added an outlet to the UIViewController:

@property (weak, nonatomic) IBOutlet NSLayoutConstraint *imageViewWidthConstraint;

then on viewDidLayoutSubviews I updated the constraint:

- (void) viewDidLayoutSubviews {
    [super viewDidLayoutSubviews];

    self.imageViewWidthConstraint.constant = CGRectGetWidth(self.scrollView.frame);
}

This seemed to do the trick.