Adding Right Aligning Constraints to the Programmatically Added Subview - ios

Question

I am trying to add a right aligned Segmented Control to the `UITableViewCell like this:
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = UITableViewCell(style: UITableViewCellStyle.default, reuseIdentifier: "mycell")
// ...
addSegmentedControlToCell(cell)
// ...
and then
func addSegmentedControlToCell(_ cell:UITableViewCell){
let items = ["One","Two"]
let unitControl = UISegmentedControl(items: items)
unitControl.selectedSegmentIndex = 0
let maxWd = cell.frame.size.width
let maxHt = cell.frame.size.height
let padding:CGFloat = 5
unitControl.frame = CGRect(x:maxWd/2, y:padding, width:maxWd/2, height: maxHt-padding*2)
unitControl.addTarget(self, action: #selector(SettingsTableViewController.unitControlValueDidChange(_:)), for: .valueChanged)
cell.addSubview(unitControl)
}
This works well on my default device iPhone 6. But when I run this app on a smaller width device, like iPhone 5, the programmatically added Segment Control, which receives 50% of cell width (cell.frame.size.width/2) seems much bigger that 50% of width and stretches to the right under the cell view port.
This is because of auto-layout and constraints as I see because iPhone 5 cell view gets resized. So I am trying to add a constraint to my new Segment Control, which fails with app crush. Note, I am not very good with programmatically adding constraints yet.
let widthContr = NSLayoutConstraint(item: unitControl,
attribute: NSLayoutAttribute.width,
relatedBy: NSLayoutRelation.equal,
toItem: cell,
attribute: NSLayoutAttribute.notAnAttribute,
multiplier: 1,
constant: 0.5)
cell.addConstraints([widthContr])
How to right align subview correctly (Segment Control) for correct cell size?

Answer 1

You can set constraints like this:
yourView.rightAnchor.constraint(equalTo: yourCell.rightAnchor, constant: -10).isActive = true
Or:
yourView.heightAnchor.constraint(equalToConstant: 50).isActive = true
But make sure that you include this code:
yourSegmentedControl.translatesAutoresizingMaskIntoConstraints = false

Answer 2

You can do this in 3 ways.
1) You have written 0.5 constant in NSLayoutConstraint(this is a mistake).
You need to write constant is 1 and multiplier should be 0.5.
2) Or you should update frame of UISegmentControl in layoutSubviews() method of Custom Cell.
3) Or you should write cell.layoutSubviews() after UISegmentControl adding to Cell.