chrsp

extension Reactive where Base == UIScreen {
    @available(iOS 13.0, *)
    func userInterfaceStyle() -> Observable<UIUserInterfaceStyle> {
        let currentUserInterfaceStyle = UITraitCollection.current.userInterfaceStyle
        let initial = Observable.just(currentUserInterfaceStyle)
        let selector = #selector(UIScreen.traitCollectionDidChange(_:))
        let following = self.base
            .rx
            .methodInvoked(selector)
            .flatMap { (args) -> Observable<UIUserInterfaceStyle> in

chrsp

// Only contents of UIKit can use DynamicColors. So if you need the dynamic color behavior 
// on CALayer, CGColor etc you need to use one of these 3 options:

// Option 1
let resolvedColor = UIColor.label.resolvedColor(with: traitCollection)
layer.borderColor = resolvedColor.cgColor

// Option 2
traitCollection.perfomAsCurrent {
  layer.borderColor = UIColor.label.cgColor

chrsp

    func isNifValid(nif: String) -> Bool {
        
        guard nif.count == 9, let nifPrefix = Int(nif.prefix(1)) else { return false }
        
        if [1, 2, 5, 6, 9].contains(nifPrefix) {
            var checkDigit = nifPrefix * 9
            
            for index in 2...nif.count - 1 {
                let indexBound = nif.index(nif.startIndex, offsetBy: index - 1)
                checkDigit += (Int(String(nif[indexBound])) ?? 0) * (10 - index)