How to create a user defined countdown timer in Swift?

Question

How can I create a user defined countdown timer in Swift?

I got 2 pages in my app. On first page I ask user to write in UITextField a value as hour (for ex: 3), then with segue.identifier, I pass this information to second page, and I want to make a countdown from 3 hours as 02:59:59 format and print it in UILabel. Thanks

Answer 1

I made you a playground with an example of countdown with a NSTimer.

import UIKit

class MyClass {

  var timerCounter:NSTimeInterval!

  func stringFromTimeInterval(interval: NSTimeInterval) -> String {
    let interval = Int(interval)
    let seconds = interval % 60
    let minutes = (interval / 60) % 60
    let hours = (interval / 3600)
    return String(format: "%02d:%02d:%02d", hours, minutes, seconds)
  }

  func startTimer(hour:Int) {
    timerCounter = NSTimeInterval(hour * 60 * 60)
    NSTimer.scheduledTimerWithTimeInterval(1, target: self, selector: "onTimer:", userInfo: nil, repeats: true)
  }

  @objc func onTimer(timer:NSTimer!) {
    // Here is the string containing the timer
    // Update your label here
    println(stringFromTimeInterval(timerCounter))
    timerCounter!--
  }
}

var anInstance = MyClass()

// Start timer with 3 hours
anInstance.startTimer(3)
CFRunLoopRun()