swift-3.0 将HexColor转变为UIColor的方法

// MARK:- 把#ffffff颜色转为UIColor
extension UIColor {
    class func colorWithHexString(hex:String) ->UIColor {
        
        var cString = hex.trimmingCharacters(in:CharacterSet.whitespacesAndNewlines).uppercased()
        
        if (cString.hasPrefix("#")) {
            let index = cString.index(cString.startIndex, offsetBy:1)
            cString = cString.substring(from: index)
        }
        
        if (cString.characters.count != 6) {
            return UIColor.red
        }
        
        let rIndex = cString.index(cString.startIndex, offsetBy: 2)
        let rString = cString.substring(to: rIndex)
        let otherString = cString.substring(from: rIndex)
        let gIndex = otherString.index(otherString.startIndex, offsetBy: 2)
        let gString = otherString.substring(to: gIndex)
        let bIndex = cString.index(cString.endIndex, offsetBy: -2)
        let bString = cString.substring(from: bIndex)
        
        var r:CUnsignedInt = 0, g:CUnsignedInt = 0, b:CUnsignedInt = 0;
        Scanner(string: rString).scanHexInt32(&r)
        Scanner(string: gString).scanHexInt32(&g)
        Scanner(string: bString).scanHexInt32(&b)
        
        return UIColor(red: CGFloat(r) / 255.0, green: CGFloat(g) / 255.0, blue: CGFloat(b) / 255.0, alpha: CGFloat(1))
    }
}