如何找到两次之间的时间跨度？

Question

我想计算剩余时间.我有一个完成时间.如何计算现在和结束时间之间的剩余时间？

我需要这样的东西

let date = NSDate()
let formatter = NSDateFormatter()
formatter.timeStyle = .ShortStyle
var now = formatter.stringFromDate(date) //prints 12.21 AM
var finishTime = "13:30 PM"

var remaining = now - finishTime //I want it to print 01:09 as remaining time

Answer 1

func timeRemainingString(finishDate date:NSDate) -> String {
    let secondsFromNowToFinish = date.timeIntervalSinceNow
    let hours = Int(secondsFromNowToFinish / 3600)
    let minutes = Int((secondsFromNowToFinish - Double(hours) * 3600) / 60)
    let seconds = Int(secondsFromNowToFinish - Double(hours) * 3600 - Double(minutes) * 60 + 0.5)

    return String(format: "%02d:%02d:%02d", hours, minutes, seconds)
}