Counter-Swift

ViewController.swift

import UIKit

class ViewController: UIViewController {
    
    @IBOutlet weak var display: UILabel?
    
    @IBAction func add(sender: UIButton) {
        count++
    }
    
    var count:Int = 0 {
        didSet {
            display?.text = String(count)
        }
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        count = 0;
    }
}