(Swift) NSTimer count

ViewController.swift

import UIKit

class ViewController: UIViewController {
    
    var timer = NSTimer()
    var count = 0

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        timer = NSTimer(timeInterval: 2.0, target: self, selector: "countUp", userInfo: nil, repeats: true)
        NSRunLoop.currentRunLoop().addTimer(timer, forMode: NSRunLoopCommonModes)
    }
    
    func countUp() {
        count++
        print("\(count)")
    }
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}