UIView extension - Fallback Constraints

gistfile1.swift

view.addFallbackConstraints(item: labelB, attribute: .Top, relatedBy: .Equal, fallbackArrayItems:[topImageView], attribute: .Bottom, multiplier: 1, constant: 20, startPriority:110)
view.addFallbackConstraints(item: labelC, attribute: .Top, relatedBy: .Equal, fallbackArrayItems:[labelA,topImageView], attribute: .Bottom, multiplier: 1, constant: 20, startPriority:105)
view.addFallbackConstraints(item: labelD, attribute: .Top, relatedBy: .Equal, fallbackArrayItems:[labelB,labelA,topImageView], attribute: .Bottom, multiplier: 1, constant: 20, startPriority:100)


extension UIView {

    func addFallbackConstraints(item view1: AnyObject, attribute attr1: NSLayoutAttribute, relatedBy relation: NSLayoutRelation, fallbackArrayItems: [AnyObject], attribute attr2: NSLayoutAttribute, multiplier: CGFloat = 1, constant c: CGFloat, startPriority: UILayoutPriority) -> UILayoutPriority {
        var priorityDecrementer = startPriority

        for item in fallbackArrayItems {
            var constraint = NSLayoutConstraint(item: view1, attribute: attr1, relatedBy: relation, toItem: item, attribute: attr2, multiplier: multiplier, constant: c)
            constraint.priority = priorityDecrementer--

            self.addConstraint(constraint)
        }
        return priorityDecrementer
    }
}