How to make my iphone vibrate twice when I click on a button?

Update for iOS 10

With iOS 10, there are a few new ways to do this with minimal code.

Method 1 - UIImpactFeedbackGenerator:

let feedbackGenerator = UIImpactFeedbackGenerator(style: .heavy)
feedbackGenerator.impactOccurred()

Method 2 - UINotificationFeedbackGenerator:

let feedbackGenerator = UINotificationFeedbackGenerator()
feedbackGenerator.notificationOccurred(.error)

Method 3 - UISelectionFeedbackGenerator:

let feedbackGenerator = UISelectionFeedbackGenerator()
feedbackGenerator.selectionChanged()

#import <AudioToolbox/AudioServices.h>


AudioServicesPlayAlertSound(UInt32(kSystemSoundID_Vibrate))

This is the swift function...See this article for detailed description.

This is what I came up with:

import UIKit
import AudioToolbox

class ViewController: UIViewController {

    var counter = 0
    var timer : NSTimer?

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }

    func vibratePhone() {
        counter++
        switch counter {
        case 1, 2:
            AudioServicesPlaySystemSound(kSystemSoundID_Vibrate)
        default:
            timer?.invalidate()
        }
    }

    @IBAction func vibrate(sender: UIButton) {
        counter = 0
        timer = NSTimer.scheduledTimerWithTimeInterval(0.6, target: self, selector: "vibratePhone", userInfo: nil, repeats: true)
    }
}

When you press the button, the timer starts and repeats at desired time interval. The NSTimer calls the vibratePhone(Void) function and from there I can control how many times the phone will vibrate. I used a switch in this case, but you could use a if else, too. Simply set a counter to count each time the function is called.