Question

我可以在日期选择器中获取日期，计算剩余时间并放入标签。这给了秒：

let timeLeft = datePicker.dateValue.timeIntervalSinceNow
countingLabel.stringValue = "seconds left: \(timeLeft)"

如何格式化“timeLeft”？

I tried this and it does not work:
var formatter = NSDateFormatter()
formatter.dateFormat = "EEEE, yyyy-MM-dd hh:mm:ss"
let timeLeft2 = formatter.stringFromDate(timeLeft)

Answer 1

您可以使用NSDateComponentsFormatter。来自文档：

NSDateComponentsFormatter对象需要花费大量时间和将它们格式化为用户可读的字符串。使用日期组件 formatter为您的应用程序界面创建字符串。

示例：

let formatter = NSDateComponentsFormatter()
formatter.unitsStyle = .Full
formatter.allowedUnits = .CalendarUnitSecond | .CalendarUnitMinute | .CalendarUnitHour

let pickedDate = datePicker.dateValue
let now = NSDate()
let formattedTimeLeft = formatter.stringFromDate(now, toDate: pickedDate)!

// Example result : 1:06:50

还有一些可用的输出格式，例如

.Abbreviated :  1h 6m 50s
.Short :        1 hr, 6 min, 50 secs
.Full :         1 hour, 6 minutes and 50 seconds

Answer 2

要获得timeLeft，您应该使用两个时间组件并获得如下差异：

let todayComponents = NSCalendar.currentCalendar().components(.DayCalendarUnit | .MonthCalendarUnit | .YearCalendarUnit | .CalendarUnitHour | .CalendarUnitMinute | .CalendarUnitSecond | , fromDate : NSDate())

var pickedDateComponents = NSCalendar.currentCalendar().components(.DayCalendarUnit | .MonthCalendarUnit | .YearCalendarUnit | .CalendarUnitHour | .CalendarUnitMinute | .CalendarUnitSecond | , fromDate : datePicker.dateValue)

pickedDateComponents.second  =  pickedDateComponents.second - todayComponents.second 
pickedDateComponents.minute = pickedDateComponents.minute - todayComponents.minute 
pickedDateComponents.hour = pickedDateComponents.hour - todayComponents.hour 
pickedDateComponents.day =pickedDateComponents.day - todayComponents.day 
pickedDateComponents.month = pickedDateComponents.month - todayComponents.month 
pickedDateComponents.year = pickedDateComponents.year - todayComponents.year 

let timeLeft = NSCalendar.currentCalendar().dateFromComponents(pickedDateComponents)!

Swift timeInterval格式化程序

2 个答案: