Centering a view with auto constraints - Swift - swift

Question

I am creating an XIB/class of datePicker which is called programatically from a calling viewController when the user taps a button. How can I use auto constraints to place this view immediately below and aligned with the centre of the calling button. My code works in portrait, but fails when the device is rotated (the datePicker does not re-center). Probably because I am passing a CGRect as an argument on init of the view, which doesn't change on rotate. I can't see any other way of overriding the passing of CGRect. When I add in auto constraints code, I get run-time auto formatting errors.
ViewController:
#IBAction func showMyDatePicker(_ sender: Any) {
showMyDatePicker.isEnabled = false
let today = Date()
let minDate = Calendar.current.date(byAdding: .month, value: -3, to: today)
let maxDate = Calendar.current.date(byAdding: .month, value: 3, to: today)
let datePickerWidth = 300
let datePickerHeight = 200
let datePickerX = Int(showMyDatePicker.center.x - CGFloat(datePickerWidth / 2))
let datePickerY = Int(showMyDatePicker.center.y + CGFloat(showMyDatePicker.bounds.height / 2))
let frame = CGRect(x: datePickerX, y: datePickerY, width: datePickerWidth, height: datePickerHeight)
myDatePicker = MyDatePicker(frame: frame)
myDatePicker?.setMyDatePicker(date: today, minimumDate: minDate!, maximumDate: maxDate!)
myDatePicker?.delegate = self
self.view.addSubview(myDatePicker!)
}
datePickerClass:
class MyDatePicker: UIView {
var delegate: MyDatePickerDelegate?
#IBOutlet var contentView: UIView!
#IBOutlet weak var datePicker: UIDatePicker!
#IBOutlet weak var returnButton: UIButton!
#IBAction func datePickerChanged(_ sender: Any) {
delegate?.dateFromDatePicker(date: datePicker.date, closeDatePickerView: false)
}
#IBAction func returnButtonTapped(_ sender: Any) {
delegate?.dateFromDatePicker(date: datePicker.date, closeDatePickerView: true)
}
override init(frame: CGRect) {
super.init(frame: frame)
initView()
}
required init?(coder: NSCoder) {
super.init(coder: coder)
initView()
}
private func initView() {//QUESTION: how can I set the datepicker initial values within here
// Instantiate the view from xib file
let contentView = Bundle.main.loadNibNamed("MyDatePicker", owner: self, options: nil)?.first as? UIView
// Check that it's not nil
guard contentView != nil else {
return
}
// Add the view and set its frame
addSubview(contentView!)
contentView?.frame = self.bounds
contentView?.autoresizingMask = [.flexibleHeight, .flexibleWidth]
}
func setMyDatePicker(date: Date, minimumDate: Date, maximumDate: Date) {
datePicker.date = date
datePicker.minimumDate = minimumDate
datePicker.maximumDate = maximumDate
}
}

Answer 1

Just add the required constraint after addSubview and setting TAMIC to false as follows:
#IBAction func showMyDatePicker(_ sender: UIButton) {
// ...
view.addSubview(myDatePicker!)
myDatePicker.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
myDatePicker.topAnchor.constraint(equalTo: sender.bottomAnchor),
myDatePicker.centerXAnchor.constraint(equalTo: sender.centerXAnchor)])
}