斯威夫特：日期选择器定时器？答案

【问题标题】：Swift: DatePicker-Timer?斯威夫特：日期选择器定时器？
【发布时间】：2020-06-16 15:21:20
【问题描述】：

嘿！

这是我的问题：

所以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），直到时间到达。最好采用格式 (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：/

如果有人可以帮助我，我会很高兴！

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"

【问题讨论】：

标签： swift xcode timer datepicker countdown

【解决方案1】：

首先，你不能写：

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

如果competitionDate 不是DateComponents 而是Date，它只会触发错误！

那么，如果您只想要时间量的字符串表示，DateComponentsFormatter 适合您

试试：

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"

【讨论】：