Chronometer-3.swift

   // Animation values creator (1)
struct PulseConfiguration {
    // static values
    private var scaleChangeAmount:CGFloat = 0.015
    private var maxScale:CGFloat = 1.5
    private var minScale:CGFloat = 1
    
    // dynamic Values
    private var currentScale:CGFloat = 1
    private var isExpanding:Bool = true
    
    init(scaleChangeAmount:CGFloat =  0.015  , minScale:CGFloat = 1.5 , maxScale:CGFloat = 1) {
        self.scaleChangeAmount = scaleChangeAmount
        self.minScale = minScale
        self.maxScale = maxScale
    }
    
    mutating func scale(_currentScale:CGFloat? = nil)->CGFloat {
        if let sc = _currentScale { currentScale = sc }
        let scaleChangeValue = isExpanding == true ? scaleChangeAmount : (-1) * scaleChangeAmount
        currentScale += scaleChangeValue
        if currentScale >= maxScale { isExpanding = false }
        else if currentScale <= minScale { isExpanding = true }
        return currentScale
    }
}


    
    private var currentPulseConfig:PulseConfiguration = PulseConfiguration()

    displayLink?.displayLinkUpdated = { timeInterval in
           ...
           self.updatePulsingLayer(timeInterval: timeInterval)
     }


    private func updatePulsingLayer(timeInterval:CFTimeInterval) {
        pulsatingLayer.transform = CATransform3DMakeScale(currentPulseConfig.scale(), currentPulseConfig.scale(), 1)
    }
    

// Tests 
//(2a)
func test1PulsatingAnimationWorksCoool() {
        var pulsatingConfig = PulseConfiguration(scaleChangeAmount: 0.5, minScale: 1, maxScale: 2)
        var scale = pulsatingConfig.scale(_currentScale: 1)
        XCTAssert(scale == 1.5)
        scale = pulsatingConfig.scale()
        scale = pulsatingConfig.scale()
        XCTAssert(scale == 1.5)
        scale = pulsatingConfig.scale()
        scale = pulsatingConfig.scale()
        XCTAssert(scale == 1.5)
    }