swift - 如何让这段代码秒到秒倒计时？

Question

我有这段倒计时代码，但它不会每秒刷新一次。它只是在加载后立即暂停。如何让它每秒刷新一次以显示秒到秒的倒计时？

var dateComponents = NSDateComponents()

    dateComponents.day = 25
    dateComponents.month = 12
    dateComponents.year = 2015
    dateComponents.second = 0

       let christmasDay = NSCalendar(identifier: NSCalendarIdentifierGregorian)!.dateFromComponents(dateComponents)!

     let durationDateComponents = NSCalendar(identifier: NSCalendarIdentifierGregorian)!.components( [.Year, .Month, .Day, .Hour, .Minute, .Second], fromDate: NSDate(), toDate: christmasDay, options: [])

    minUntilHoliday.text =  "\(durationDateComponents.minute) months and"

    secUntilHoliday.text = "\(durationDateComponents.second) days."

Answer 1

你可以把它放到一个函数中:

func callEverySecond() {
     var dateComponents = NSDateComponents()
     dateComponents.day = 25
     dateComponents.month = 12
     dateComponents.year = 2015
     dateComponents.second = 0

     let christmasDay = NSCalendar(identifier: NSCalendarIdentifierGregorian)!.dateFromComponents(dateComponents)!

     let durationDateComponents = NSCalendar(identifier: NSCalendarIdentifierGregorian)!.components( [.Year, .Month, .Day, .Hour, .Minute, .Second], fromDate: NSDate(), toDate: christmasDay, options: [])

     minUntilHoliday.text =  "\(durationDateComponents.minute) months and"

     secUntilHoliday.text = "\(durationDateComponents.second) days."
}

然后，使用 NSTimer 调用该函数(在您的 viewDidLoad 中):

let timeTimer = NSTimer.scheduledTimerWithTimeInterval(1, target: self, selector: "callEverySecond", userInfo: nil, repeats: true)