Autolayout & programmatic constraints: How to deal with updateConstraints firing multiple times?

Question

When programmatically creating layouts, I follow Apple\'s advice: override -updateConstraints, add custom constraints, and call -setNeedsUpdateConstraints once subviews have

Answer 1

This kind of tracking could be done too, for the initial setup. In most cases.

override func updateConstraints() {
            if constraints.count == 0 {
                let views = ["textField": textField]
                addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:|-0-[textField]-0-|", options: [], metrics: nil, views: views))
                addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|-0-[textField]-0-|", options: [], metrics: nil, views: views))
            }
            super.updateConstraints()
        }