Change color of UISwitch in “off” state

Question

I\'ve learned that we can change the UISwitch button appearance in its \"on\" state, but is it also possible to change the color of the UISwitch in the \"off\" state?

Answer 1

XCode 11, Swift 4.2

Starting with Matt's solution I added it to a custom, IBDesignable control. There is a timing issue in that didMoveToSuperview() is called before the offTintColor is set that needed to be handled.

@IBDesignable public class UISwitchCustom: UISwitch {

    var switchMask: UIImageView?
    private var observers = [NSKeyValueObservation]()

    @IBInspectable dynamic var offTintColor : UIColor! = UIColor.gray {
        didSet {
             switchMask?.tintColor = offTintColor
        }
    }

    override init(frame: CGRect) {
        super.init(frame: frame)
        initializeObservers()
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        initializeObservers()
    }

    private func initializeObservers() {
        observers.append(observe(\.isHidden, options: [.initial]) {(model, change) in
            self.switchMask?.isHidden = self.isHidden
        })
    }

    override public func didMoveToSuperview() {
        addOffColorMask(offTintColor)
        super.didMoveToSuperview()
    }

   private func addOffColorMask(_ color: UIColor) {
        guard self.superview != nil else {return}
        let onswitch = UISwitch()
        onswitch.isOn = true
        let r = UIGraphicsImageRenderer(bounds:self.bounds)
        let im = r.image { ctx in
            onswitch.layer.render(in: ctx.cgContext)
            }.withRenderingMode(.alwaysTemplate)
        let iv = UIImageView(image:im)
        iv.tintColor = color
        self.superview!.insertSubview(iv, belowSubview: self)
        iv.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            iv.topAnchor.constraint(equalTo: self.topAnchor),
            iv.bottomAnchor.constraint(equalTo: self.bottomAnchor),
            iv.leadingAnchor.constraint(equalTo: self.leadingAnchor),
            iv.trailingAnchor.constraint(equalTo: self.trailingAnchor),
            ])
        switchMask = iv
        switchMask?.isHidden = self.isHidden
    }

}