     public required init?(coder aDecoder: NSCoder) {
         super.init(coder: aDecoder)
         
-        self.fadeDuration = aDecoder.decodeFloat(forKey: "FadeDuration")
+        self.fadeDuration = aDecoder.decodeDouble(forKey: "FadeDuration")
         self.overlayImageView = aDecoder.decodeObject(forKey: "OverlayImageView") as! UIImageView // swiftlint:disable:this force_cast
         self.overlayImageView.frame = self.imageView!.frame
         self.overlayImageView.bounds = self.imageView!.bounds

    ///   - image: Button image.
    ///   - highlightedImage: Button highlighted image.
    ///   - fadeDuration: Fade duration.
    public init(frame: CGRect, image: UIImage, highlightedImage: UIImage, fadeDuration: Float) {
        self.fadeDuration = fadeDuration
        
        super.init(frame: frame)

    // MARK: - Variables
    
    /// The fade duration.
    public var fadeDuration: TimeInterval = 0
    
    /// The animation on highlighted status.
    open override var isHighlighted: Bool {
