swift 之 URL编码

func encodeEscapesURL(value:String) -> String {
        let str:NSString = value
        let originalString = str as CFStringRef
        let charactersToBeEscaped = "!*'();:@&=+$,/?%#[]" as CFStringRef  //":/?&=;+!@#$()',*" //转意符号
        //let charactersToLeaveUnescaped = "[]." as CFStringRef //保留的符号
        let result =
        CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault,originalString,nil,//charactersToLeaveUnescaped,
            charactersToBeEscaped,CFStringConvertNSStringEncodingToEncoding(NSUTF8StringEncoding)) as NSString

        return result as String
    }