Animating NSLayoutConstraint in didSelectRowAtIndexPath doesn't work - ios

Question

I have a MainVC(UIViewController) with a MainTableVC(UITableView) and another nested SubTableVC(UITableView).
Both of them has the MainVC as its delegate and dataSource, also, each one has its own restorationIdentifier so I can distinguish between them when I call a delegate or dataSource function.
Here's an example:
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
switch tableView.restorationIdentifier {
case "MainTableVCID":
return 10
case "SubTableVC":
return 5
default:
return 0
}
}
That's working perfectly great. But one issue I have here and I couldn't solve is:
I have a UIPickerView that's a subview of the MainVC's view, it's constrained just below the MainVC's view with constraints like this:
private let pickerView: UIPickerView = {
let picker = UIPickerView()
picker.backgroundColor = UIColor.lightGray
picker.translatesAutoresizingMaskIntoConstraints = false
return picker
}()
private var pickerViewBottomAnchor: NSLayoutConstraint?
override func viewDidLoad() {
super.viewDidLoad()
//other init code..
view.addSubview(pickerView)
pickerView.widthAnchor.constraint(equalTo: view.widthAnchor).isActive = true
pickerView.heightAnchor.constraint(equalToConstant: 180).isActive = true
pickerViewBottomAnchor = pickerView.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: 180)
pickerViewBottomAnchor?.isActive = true
pickerView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
}
In the nested tableView (SubTableVC), in tableView:didSelectRowAtIndexPath: I want to animate the NSLayoutConstraint's constant to be equal to Zero.
However, at this time, I get pickerViewBottomAnchor = nil when I use console to print object (po self. pickerViewBottomAnchor?.constant) //prints nil.
Here's the code I use:
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
if tableView.restorationIdentifier == "SubTableVC" {
pickerViewBottomAnchor?.constant = 180
self.view.layoutIfNeeded()
}
}

Answer 1

Start with changing your didSelectRowAt function to:
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
if pickerViewBottomAnchor?.constant != 0 {
pickerViewBottomAnchor?.constant = 0
} else {
pickerViewBottomAnchor?.constant = 180
}
UIView.animate(withDuration: 0.5) {
self.view.layoutIfNeeded()
}
}
Using that, selecting a row in either table should alternately slide the picker view up or down.
If that doesn't do anything, then you (likely) do not have your table views .delegate property set correctly.
If / when that does work, edit the function to only act when you've selected a row on the subTableView