UIColor+HexString.swift

extension UIColor{
    convenience init (hexString:String) {
        let cleanString = hexString.stringByTrimmingCharactersInSet(NSCharacterSet.alphanumericCharacterSet().invertedSet)
        
        var rgbValue = UInt32()
        NSScanner(string: cleanString).scanHexInt(&rgbValue)
        let a,r,g,b:UInt32
        
        switch cleanString.characters.count{
        case 3: // RGB (12-bit)
            (a, r, g, b) = (255, (rgbValue >> 8) * 17, (rgbValue >> 4 & 0xF) * 17, (rgbValue & 0xF) * 17)
        case 6: // RGB (24-bit)
            (a, r, g, b) = (255, rgbValue >> 16, rgbValue >> 8 & 0xFF, rgbValue & 0xFF)
        case 8: // ARGB (32-bit)
            (a, r, g, b) = (rgbValue >> 24, rgbValue >> 16 & 0xFF, rgbValue >> 8 & 0xFF, rgbValue & 0xFF)
        default:
            (a, r, g, b) = (1, 1, 1, 0)
        }
        
        self.init(
            red:    CGFloat(r)/255,
            green:  CGFloat(g)/255,
            blue:   CGFloat(b)/255,
            alpha:  CGFloat(a)/255)
    }
}