UILabel addAttributedString

extension UILabel {
    
    func addAttributedString (text: String, color: UIColor, font: UIFont) {
        var string = self.text == nil ? "" : self.text!
        let newString = string + text
        let range = NSRange(location: countElements(string), length: countElements(text))
        var att: NSMutableAttributedString?
        
        if let a = self.attributedText {
            att = NSMutableAttributedString (attributedString: a)
            att?.appendAttributedString(NSAttributedString (string: text))
        } else {
            att = NSMutableAttributedString (string: newString)
        }
        
        att!.addAttribute(NSFontAttributeName, value: font, range: range)
        att!.addAttribute(NSForegroundColorAttributeName, value: color, range: range)
        
        self.attributedText = NSAttributedString (attributedString: att!)
    }
    
}