iOS - Find top constraint for a view?

Question

I am trying to find the top constraint of the view in code. The top constraint is added in storyboard, and I don\'t want to use an IBOutlet.

Logging the value of the

Answer 1

Here's a one-liner extension method, based on @Igor's approach:

extension UIView{

    func constraint(for layoutAttribute: NSLayoutConstraint.Attribute) -> NSLayoutConstraint? {
        return superview?.constraints.first { itemMatch(constraint: $0, layoutAttribute: layoutAttribute) }
    }

    private func itemMatch(constraint: NSLayoutConstraint, layoutAttribute: NSLayoutConstraint.Attribute) -> Bool {
        if let firstItem = constraint.firstItem as? UIView, let secondItem = constraint.secondItem as? UIView {
            let firstItemMatch = firstItem == self && constraint.firstAttribute == layoutAttribute
            let secondItemMatch = secondItem == self && constraint.secondAttribute == layoutAttribute
            return firstItemMatch || secondItemMatch
        }
        return false
    }
}

[ I also made the method signature style to match Swift 3...5 style e.g.:

constraint(for:) instead of findConstraint(layoutAttribute:). ]