Swift Update Constraint

Question

I added the constraint to the buttons created in my UIView

func CreateButtonWithIndex(index:Int) {

    newButton.setTranslatesAutoresizingMaskI         


        

Answer 1

Update Rob's Answer to Swift 3:

class ViewController: UIViewController {

    private var xConstraint: NSLayoutConstraint!
    private var yConstraint: NSLayoutConstraint!

    override func viewDidLoad() {
    super.viewDidLoad()

    let label = UILabel()
    label.text = "x"
    label.setTranslatesAutoresizingMaskIntoConstraints(false)
    view.addSubview(label)

    // I don't really need to save references to these, so these are local variables


    let widthConstraint = NSLayoutConstraint(item: drugToDrugView, attribute: .width, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1.0, constant: 50)
    let heightConstraint = NSLayoutConstraint(item: drugToDrugView, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1.0, constant: 50)

    // but since I'll be modifying these later, these are class properties

    xConstraint = NSLayoutConstraint(item: drugToDrugView, attribute: .centerX, relatedBy: .equal, toItem: view, attribute: .centerX, multiplier: 1.0, constant: 0)
    yConstraint = NSLayoutConstraint(item: drugToDrugView, attribute: .centerY, relatedBy: .equal, toItem: view, attribute: .centerY, multiplier: 1.0, constant: 0)

    drugToDrugView.addConstraints([widthConstraint, heightConstraint, xConstraint, yConstraint])

    let pan = UIPanGestureRecognizer(target: self, action: #selector(handlePan))
    view.addGestureRecognizer(pan)

 }

 private var originalCenter: CGPoint!

 func handlePan(gesture: UIPanGestureRecognizer) {
    if gesture.state == .began {
        originalCenter = CGPoint(x: xConstraint.constant, y: yConstraint.constant)
    }

    let translation = gesture.translation(in: gesture.view!)

    xConstraint.constant = originalCenter.x + translation.x
    yConstraint.constant = originalCenter.y + translation.y
    view.setNeedsLayout()
}