Counting Label

WCCountingLabel.swift

import UIKit

class WCCountingLabel: UILabel {
    
    private var start: CGFloat = 0
    private var end: CGFloat = 0
    private var progress: NSTimeInterval = 0
    private var lastUpdate: NSTimeInterval = 0
    private var totalTime: NSTimeInterval = 0
    private var easingRate: CGFloat = 0
    
    private var timer: CADisplayLink = CADisplayLink()
    
    func countFrom(startValue: CGFloat, toEndValue endValue: CGFloat, withDuration duration: NSTimeInterval) {
        start = startValue
        end = endValue
        
        
//        timer.invalidate()
        
        if duration == 0.0 {
            setTextValue(endValue)
            return
        }
        
        easingRate = 3.0
        progress = 0
        totalTime = duration
        lastUpdate = NSDate.timeIntervalSinceReferenceDate()
        
        let displayLink = CADisplayLink(target: self, selector: #selector(WCCountingLabel.updateValue(_:)))
        displayLink.frameInterval = 2
        displayLink.addToRunLoop(NSRunLoop.mainRunLoop(), forMode: NSDefaultRunLoopMode)
        displayLink.addToRunLoop(NSRunLoop.mainRunLoop(), forMode: UITrackingRunLoopMode)
        timer = displayLink
    }
    
    func setTextValue(endValue: CGFloat) {
        let intValue = Int(endValue)
        let numberFormatter = NSNumberFormatter()
        numberFormatter.numberStyle = .DecimalStyle
        text = numberFormatter.stringFromNumber(intValue) ?? ""
    }
    
    func updateValue(timer: NSTimer) {
        let now = NSDate.timeIntervalSinceReferenceDate()
        progress = progress + now - lastUpdate
        lastUpdate = now
        if progress >= totalTime {
            timer.invalidate()
            progress = totalTime
        }
        setTextValue(currentValue())
    }
    
    func currentValue() -> CGFloat {
        if progress >= totalTime {
            return end
        }
        let percent = CGFloat(progress) / CGFloat(totalTime)
        return start + (percent * (end - start))
    }
}