嘿！
这是我的问题：
所以我有一个日期选择器，它主要用于在达到设定的时间后发送消息。但是，我希望看到时间用完（类似于计时器），直到到达时间为止。最好采用（hh：mm：ss）格式，因为日期选择器是以计时器格式设置的。
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，我将非常高兴！
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"
首先，你只是不能写：
let competition = userCalendar.date(from: competitionDate as DateComponents)!
如果competitionDate不是DateComponents而是说Date，它只会触发错误！
然后，如果您只想要时间DateComponentsFormatter的字符串表示形式适合您
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"
欢迎您加入。这样的事情怎么样：
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head><meta http-equiv="content-type" content="text/html; charset=utf-8">
<title>Timer Demo</title>
</head>
<body>
<div style="background-color: yellow;">A Minunte passing by as a percentage.</div>
<div id='percentage' style="background-color: lime;">Timer percentage!</div>
</body>
<script>
// End in 2h.
let end = Date.now() + 7200 * 1000;
function pad(s)
{
while (s.length < 2) { s = '0' + s; }
return s;
}
/** setInterval allows to define a function like this anonymous one.
* This will be called after each interval defined in milli seconds as
* the second parameter. (Here 1000ms)
* The second paramter is the number of milliseconds that passes between */
window.setInterval(function()
{
let div = document.getElementById('percentage');
let now = Date.now();
let diff = (end - now) / 1000.;
let hours = Math.trunc(diff / 3600);
diff = diff - (hours * 3600);
let minutes = Math.trunc(diff / 60);
diff = diff - (minutes * 60);
let seconds = Math.trunc(diff);
div.innerHTML = pad(String(hours)) + ':' + pad(String(minutes)) + ':' + pad(String(seconds));
}, 1000.);
</script>
</html>
此示例已准备就绪。只需将其粘贴到文件中，然后将其加载到浏览器中即可。