You need to use the UIView systemLayoutSizeFittingSize: method to obtain the minimum bounding size of your header view.
I provide further discussion on using this API in this Q/A:
How to resize superview to fit all subviews with autolayout?
You need to use the UIView systemLayoutSizeFittingSize: method to obtain the minimum bounding size of your header view.
I provide further discussion on using this API in this Q/A:
How to resize superview to fit all subviews with autolayout?