how do I dynamically updated a UILabel's text programmatically

Question

I would like to use a simple function to update the text inside a UIlabel. I'm getting the error

Thread 1: Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value

I've looked into this problem and found this excellent post that suggested using optional binding/guard statements.

import UIKit

class ViewController: UIViewController {


    var mainImageView: UIImageView!
    var chooseButton: UIButton!
    var nameLabel: UILabel!

    override func loadView() {
        view = UIView()
        view.backgroundColor = .white

        let btn = UIButton(type: .custom) as UIButton
        btn.backgroundColor = .blue
        btn.layer.borderColor = UIColor.darkGray.cgColor
        btn.layer.borderWidth = 2
        btn.setTitle("Pick a side", for: .normal)
        btn.frame = CGRect(x: 100, y: 100, width: 200, height: 100)
        btn.addTarget(self, action: #selector(clickMe), for: .touchUpInside)
        btn.layer.cornerRadius = btn.frame.size.height/2
        self.view.addSubview(btn)

        let nameLabel = UILabel()

        nameLabel.text = "Here is your side"
        nameLabel.textAlignment = .center
        nameLabel.backgroundColor = .cyan
        nameLabel.frame = CGRect(x: 100, y: 400, width: 200, height: 100)
        self.view.addSubview(nameLabel)


    }

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
    }
    @objc func clickMe(sender:UIButton!) {
        print("Button Clicked")
        self.nameLabel.text = "updated title"

    }

}

Answer 1

The problem seems to be that you are adding the label manually in loadView but you are creating a local label object that you add to the view and not your class property so the class property nameLabel is always nil

Change

let nameLabel = UILabel()

to

self.nameLabel = UILabel()