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
    }