Counting up/down numbers animation - ios

Question

I have an UIPageViewController with a number in the center of each VC in it.
I want that when I swipe from view to view, the number will begin at 0 and count up until it gets to the correct number (or if the number is negative - count down) like in this gif:
https://d13yacurqjgara.cloudfront.net/users/345970/screenshots/2126044/shot.gif
How can I do that?
Thank you!

Answer 1

You can use NSTimer to achieve this.
Here is example project I created for you.
Create layout like this:
Then in your ViewController do like so:
import UIKit
class ViewController: UIViewController {
#IBOutlet var countingLabel: UILabel!
var number = 0
var destinationNumber = 30
var timer: NSTimer!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
#IBAction func startButtonTapped(sender: AnyObject) {
timer = NSTimer.scheduledTimerWithTimeInterval(0.1, target: self, selector: "countUp", userInfo: nil, repeats: true)
}
func countUp() {
if number < destinationNumber {
number += 1
countingLabel.text = "\(number)"
} else {
timer.invalidate()
}
}
}
It will work.

Answer 2

Do not overcomplicate with timers and invalidations, etc.
extension UILabel {
func countAnimation(upto: Double) {
let from: Double = text?.replace(string: ",", replacement: ".").components(separatedBy: CharacterSet.init(charactersIn: "-0123456789.").inverted).first.flatMap { Double($0) } ?? 0.0
let steps: Int = 20
let duration = 0.350
let delay = duration / Double(steps)
let diff = upto - from
for i in 0...steps {
DispatchQueue.main.asyncAfter(deadline: .now() + delay * Double(i)) {
self.text = "\(from + diff * (Double(i) / Double(delay)))"
}
}
}
}