Swift 斯威夫特：日期选择器计时器？

嘿

我的问题是：

因此，我有一个日期选择器，主要用于在达到设定时间时发送消息。但是，我希望看到时间用完（类似计时器），直到达到时间。最佳格式（hh:mm:ss），因为日期选择器设置为计时器格式

我只是编程的初学者。所以我不知道该怎么办：/

如果有人能帮助我，我会非常高兴的

非常感谢

     let date = NSDate()
     let calendar = Calendar.current

     let components = calendar.dateComponents([.hour, .minute, .month, .year, .day], from: 
     date as Date)

     let currentDate = calendar.date(from: components)

     let userCalendar = Calendar.current

     let competitionDate = self.datepicker.isSelected

     let competition = userCalendar.date(from: competitionDate as DateComponents)!

     let CompetitionDifference = calendar.dateComponents([.hour, .minute, .second], from: 
     currentDate!, to: competition)


     let hoursLeft = CompetitionDifference.hour
     let minutesLeft = CompetitionDifference.minute
     let secondsLeft = CompetitionDifference.second

     print("hours:", hoursLeft ?? "N/A", "minutes:", minutesLeft ?? "N/A", "seconds:", 
     secondsLeft ?? "N/A")

    countDownLabel.text = "\(daysLeft ?? 0) hours, \(hoursLeft ?? 0) minutes, \(minutesLeft 
    ?? 0) seconds"

---

首先，你不能写：

let competition = userCalendar.date(from: competitionDate as DateComponents)!

如果

competitionDate

不是

DateComponents

，而是

Date

，则只会触发一个错误

然后，如果您只想用字符串表示时间量，那么

尝试：

let date = Date()
let calendar = Calendar.current
let userCalendar = Calendar.current

let competitionDate = date + 4899
let comps = userCalendar.dateComponents([.year, .month, .day, .hour, .minute, .second], from: competitionDate)



let formatter = DateComponentsFormatter()
formatter.unitsStyle = .full
formatter.string(from: date, to: competitionDate) // "1 hour, 21 minutes, 39 seconds"
formatter.unitsStyle = .short
formatter.string(from: date, to: competitionDate) // "1 hr, 21 min, 39"secs"
formatter.unitsStyle = .brief
formatter.string(from: date, to: competitionDate) // "1hr 21min 39secs"
formatter.unitsStyle = .abbreviated
formatter.string(from: date, to: competitionDate) // "1h 21m 39s"
formatter.unitsStyle = .positional
formatter.string(from: date, to: competitionDate) // "1:21:39"
formatter.includesTimeRemainingPhrase = true
formatter.string(from: date, to: competitionDate) // "1:21:39 remaining"