Swift 计算时间间隔

public func dateInterval(startTime:String) -> Int{
    let dateformatter = DateFormatter()
    dateformatter.dateFormat = "yyyy-MM-dd HH:mm:ss"// 自定义时间格式
    let endTime = newDateStr()
    
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
    guard let date1 = dateFormatter.date(from: startTime),
        let date2 = dateFormatter.date(from: endTime) else {
            return -1
    }
    let components = NSCalendar.current.dateComponents([.second], from: date1, to: date2)
    //如果需要返回月份间隔，分钟间隔等等，只需要在dateComponents第一个参数后面加上相应的参数即可，示例如下：
    //    let components = NSCalendar.current.dateComponents([.month,.day,.hour,.minute], from: date1, to: date2)
    //        print(components.month!,components.day!,components.hour!,components.minute!)
    return components.second!
}