Autlolayout not updating frames by the time call to systemLayoutSizeFitting(:withHorizontalFittingPriority:verticalFittingPriority:) is made

Question

I have UITableViewCell subclass. The xib looks like below:

On launching the app I get the cell rendered as below as I change the content view with a custom lock view. The rotation from portrait to landscape is also done:

After rotating from landscape to portrait the layout is weird as below:

In the UITableViewCell subclass I have overridden the method systemLayoutSizeFitting(:withHorizontalFittingPriority:verticalFittingPriority:).

The implementation is as below:

override func systemLayoutSizeFitting(_ targetSize: CGSize, withHorizontalFittingPriority horizontalFittingPriority: UILayoutPriority, verticalFittingPriority: UILayoutPriority) -> CGSize {
        
        
        print("customContentView.bounds:", customContentView.bounds)
        
        verticalStackView.arrangedSubviews.forEach({
            $0.sizeToFit()
            $0.layoutIfNeeded()
        })

        verticalStackView.setNeedsLayout()
        verticalStackView.layoutIfNeeded()
        
       
        let customContentViewHorizontalPadding = customContentViewLeadingConstraint.constant + customContentViewTrailingConstraint.constant
        let customContentViewVerticalPadding = customContentViewTopConstraint.constant + customContentViewBottomConstraint.constant
        
        var _adjustedTargetSize = targetSize
        _adjustedTargetSize.width -= customContentViewHorizontalPadding
        _adjustedTargetSize.height -= customContentViewVerticalPadding
        var size = customContentView.systemLayoutSizeFitting(_adjustedTargetSize)

        
        let collectionViewContentSize = collectionView.collectionViewLayout.collectionViewContentSize
        size.height += collectionViewContentSize.height
        
        
        size.height += customContentViewVerticalPadding
        size.width += customContentViewHorizontalPadding
        
        return size
    }

Upon testing the rotation from landscape to portrait I have found that the target size sent in to the method has a larger width then required for portrait, which results in a smaller height calculation and messing up the interface.

Why is the system passing in a larger width then required in this rotation?. How do I correct this?

Note: If I remove the override of the method the collection view inside the stack view seems to be totally ignored in the calculation as evident with the image below:

Answer 1

systemLayoutSizeFitting is not something you override, it’s something you call. And a stack view is already self sizing from its contents so your code would be pointless in any case. As this is a table cell, just configure constraints and let the runtime size the height.