Recipe: Using Anchors to Place Views in iOS

I just learned anchors for placing views in iOS, and they totally blew my mind. If you’re setting any auto layout constraints programmatically with NSLayoutConstraint’s
constraintWithItem:attribute:relatedBy:toItem:attribute:multiplier:constant:, you know how ugly and verbose it can be –​ and you definitely want to check out anchors.

Want to center your segmented control horizontally 20 points from the top of the view? Forget NSLayoutConstraint; use anchors!

let control = UISegmentedControl(items: ["Staging", "Production"])
control.selectedSegmentIndex = 1
control.translatesAutoresizingMaskIntoConstraints = false

control.topAnchor.constraintEqualToAnchor(view.topAnchor, constant: 20).active = true
control.centerXAnchor.constraintEqualToAnchor(view.centerXAnchor).active = true

Anchors are available in iOS 9.0 and later.