swift- 时间戳转时间

    /**
    时间戳转时间
   
    :param: timestampStr  后台返回的时间戳字符串
    :param: dateFormatStr 你要得到的时间格式
   
    :returns: 返回指定格式的时间
    */
   @objc class func getTimeWithTimestamp(_ timestampStr: NSString, dateFormatStr:String) -> NSString
    {
        if timestampStr.length < 10
        {
            return ""
        }
        let s: NSString = timestampStr.substring(to: 10) as NSString
        let t: TimeInterval = s.doubleValue
        let date: Date = Date(timeIntervalSince1970: t)
       
        let formatter = DateFormatter()
        formatter.dateFormat = dateFormatStr
       
        let dateString: NSString = formatter.string(from: date) as NSString
//        println(dateString)
        return dateString
    }