Вызов метода по таймеру

Если код нужно выполнить через определенный интервал времени, поможет класс NSTimer и его статический метод scheduledTimerWithTimeInterval.

import UIKit

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()

        /* Parameters: 
             1) interval — number of seconds between firings
             2) target — object-owner of the called method
             3) selector — name of the called method
             4) userInfo — additional user info object (may be nil)
             5) repeats — timer is fired once (false) or until invalidated (true)
        */
        NSTimer.scheduledTimerWithTimeInterval(5,
                                               target: self,
                                               selector: "changeBackgroundColor:",
                                               userInfo: nil,
                                               repeats: true)
    }

    func changeBackgroundColor(timer: NSTimer) {
        // Generate random color
        let red = CGFloat(arc4random_uniform(3)) / 2
        let green = CGFloat(arc4random_uniform(3)) / 2
        let blue = CGFloat(arc4random_uniform(3)) / 2
        let alpha = CGFloat(1)
        let color = UIColor(red: red, green: green, blue: blue, alpha: alpha)

        // Animate background color changes
        UIView.animateWithDuration(1, animations: {self.view.backgroundColor = color})

        print("New background color: \(color)")

        // If the new color is white, then stop the timer
        if color == UIColor(red: 1, green: 1, blue: 1, alpha: 1) {
            timer.invalidate()

            print("The timer is stopped")
        }
    }
}