Slider-3

Slider.swift

 
final class Slider: UISlider {
 
    private let baseLayer = CALayer() // Step 3
 
    override func draw(_ rect: CGRect) {
        super.draw(rect)
        setup()
    }
 
    private func setup() {
        clear()
        createBaseLayer() // Step 3
    }
 
    private func clear() {
        tintColor = .clear
        maximumTrackTintColor = .clear
        backgroundColor = .clear
        thumbTintColor = .clear
    }
 
    // Step 3
    private func createBaseLayer() {
        baseLayer.borderWidth = 1
        baseLayer.borderColor = UIColor.lightGray.cgColor
        baseLayer.masksToBounds = true
        baseLayer.backgroundColor = UIColor.white.cgColor
        baseLayer.frame = .init(x: 0, 
                                y: frame.height / 4, 
                                width: frame.width, 
                                height: frame.height / 2)
        baseLayer.cornerRadius = baseLayer.frame.height / 2
        layer.insertSublayer(baseLayer, at: 0)
    }
}