gistfile1.txt

func setPressed(_ pressed: Bool) {
    let baseColors: [CGColor]
    let highlightColors: [CGColor]
    let rimColor: CGColor

    if pressed {
        baseColors = [...]; highlightColors = [...]
    } else {
        baseColors = [...]; highlightColors = [...]
    }

    CATransaction.begin()
    CATransaction.setDisableActions(true)
    CATransaction.setAnimationTimingFunction(CAMediaTimingFunction(name: .easeInEaseOut))
    CATransaction.setAnimationDuration(1.0)

    if animated {
        let baseAnimation = CABasicAnimation(keyPath: "colors")
        baseAnimation.fromValue = baseGradient.colors
        baseAnimation.toValue = baseColors
        baseGradient.add(baseAnimation, forKey: "colors")

        let highlightAnimation = CABasicAnimation(keyPath: "colors")
        highlightAnimation.fromValue = highlightGradient.colors
        highlightAnimation.toValue = highlightColors
        highlightGradient.add(highlightAnimation, forKey: "colors")
    }

    baseGradient.colors = baseColors
    highlightGradient.colors = highlightColors
    CATransaction.commit()
}