斯威夫特:定时器？

Question

嘿！

我的问题是：

因此，我有一个数据报警器，它主要用于在到达设定时间时发送消息。但是，我希望看到时间耗尽(就像计时器一样)，直到时间到达为止.最好采用这种格式(hh:mm:ss)，因为数据报警器是以计时器格式设置的。

我只是一个编程初学者。所以我不知道该怎么办。

如果有人能帮我，我会很高兴的！

在此之前，非常感谢您。

     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"

Answer 1

首先，你不能写：

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

如果competitionDate不是DateComponents，而是Date，它只会触发一个错误！

那么，如果您只想要字符串表示时间的数量，DateComponentsFormatter是为您准备的。

试着：

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"