Apple Swift:如何以 1/100 或 1/1000 获得当前秒数? [英] Apple Swift: how to get current seconds in 1/100 or 1/1000?

问题描述

func updateTime() {
    var date = NSDate()
    var calendar = NSCalendar.currentCalendar()
    var components = calendar.components(.CalendarUnitSecond, fromDate: date)
    var hour = components.hour
    var minutes = components.minute
    var seconds = components.second
    counterLabel.text = "\(seconds)"

    var myIndicator = counterLabel.text?.toInt()

    if myIndicator! % 2 == 0 {
        // do this
    } else {
       // do that
    }
}

我想知道如何更改此代码，以便在 counterlabel.text 中显示 1/10 或 1/100 或 1/1000 秒.就是想不通……谢谢！

I'd like to know how I can change this code so I get 1/10 or 1/100 or 1/1000 of a second to display in counterlabel.text. Just can't figure it out... thanks!

推荐答案

有一个以纳秒为单位的日历单位:

There is a calendar unit for nanoseconds:

let date = NSDate()
let calendar = NSCalendar.currentCalendar()
let components = calendar.components(.CalendarUnitNanosecond, fromDate: date)
let nanoSeconds = components.nanosecond

Swift 3 的更新

Update for Swift 3

let date = Date()
let calendar = NSCalendar.current
let components = calendar.dateComponents([.nanosecond], from: date)
let nanoSeconds = components.nanosecond

这给出了以 10^-9 秒为单位的秒的小数部分.对于毫秒，只需将此值除以 10⁶:

This gives the fractional part of the seconds in units of 10^-9 seconds. For milliseconds, just divide this value by 10⁶:

let milliSeconds = nanoSeconds / 1_000_000

或者，如果您只想显示小数秒，使用 NSDateFormatter 和 SSS 格式.示例:

Alternatively, if you just want to display the fractional seconds, use a NSDateFormatter and the SSS format. Example:

let fmt = NSDateFormatter()
fmt.dateFormat = "HH:mm:ss.SSS"
counterLabel.text = fmt.stringFromDate(date)

Swift 3 的更新

Update for Swift 3

let fmt = DateFormatter()
fmt.dateFormat = "HH:mm:ss.SSS"
counterLabel.text = fmt.stringFromDate(date)

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