How to create a timer (chrono) with NSDateFormatter? - ios

Question

This is a regular timer (chrono) with minutes and seconds.
It works fine but is there a way to have the same result with an NSDateFormatter.
var min = 0
var sec = 0
func stringFromTimeInterval(interval: NSTimeInterval) -> String {
let interval = Int(interval)
let seconds = interval % 60
let minutes = (interval / 60)
return String(format: "%2d:%02d",minutes, seconds)
}
func updateTimer(){
sec++
self.timeElapsed.text = self.stringFromTimeInterval(Double(sec))
}
Here is my attempt :
var sec = 0
func theTime(interval:NSTimeInterval) -> String {
var dateFormatter = NSDateFormatter()
var date = NSDate(timeIntervalSince1970: NSTimeInterval())
dateFormatter.dateFormat = "mm:ss"
return dateFormatter.stringFromDate(date)
}
func updateTheTime(){
sec++
self.newTimer.text = self.theTime(Double(sec))
}
I'm doing something wrong because it is always 00:00.
How can I make it work?

Answer 1

You can use NSDate and NSDateFormatter to get time string.
create an object of NSDateFormatter and NSDate, then set the style of your time to NSDateFormmatter, then call stringFromDate to get time string.
var dateFormatter = NSDateFormatter()
var date = NSDate(timeIntervalSince1970: interval)
dateFormatter.dateFormat = "mm-ss"
dateFormatter.stringFromDate(date)

Answer 2

You can use NSDateComponentsFormatter.
class ViewController: UIViewController {
// 1
var startDate: NSDate!
// 2
#IBOutlet weak var timerLabel: UILabel!
// 3
func tick() {
// 4
let elapsed = NSDate().timeIntervalSinceDate(startDate)
// 5
let formattedTime = NSDateComponentsFormatter().stringFromTimeInterval(elapsed)
// 6
timerLabel.text = formattedTime
}
// 7
#IBAction func startButtonPressed() {
// 8
startDate = NSDate()
// 9
NSTimer.scheduledTimerWithTimeInterval(1, target: self, selector: "tick", userInfo: nil, repeats: true)
}
}
Here's what's happening in that Swift code:
The startDate property will be initialized in startButtonPressed()
The timerLabel will show the output. It is a standard UILabel.
tick() will be called from an NSTimer
elapsed calculates how much time has transpired since the startDate. NSDate() is a handy way to get the current date.
This is where the magic happens. The NSDateComponentsFormatter will output a correctly trimmed String for the elapsed time.
The formattedTime is displayed on the screen
startButtonPressed() is called when the user taps the Start button.
The startDate property is set to the current date.
An NSTimer will call tick() every 1 second.
Here's a screenshot of what it looks like in practice with:
four seconds elapsed
one minute and four seconds elapsed