Animate

animate.swift

func animate(for duration: CGFloat, loop: @escaping (CGFloat) -> (), done: @escaping () -> ()) {
    let startTime = Date()
    RunLoop.current.add(Timer(timeInterval: 1.0 / Double(UIScreen.main.maximumFramesPerSecond), repeats: true, block: { t in
        let elapsedTime = CGFloat(-startTime.timeIntervalSinceNow)
        let fraction = min(elapsedTime / duration, 1.0)
        loop(fraction)
        if fraction == 1.0 {
            done()
            t.invalidate()
        }
    }), forMode: .common)
}