Swift：无法将“NSDate”类型的值转换为预期的参数类型“NSDateComponents”

Question

有人知道我该如何解决这个问题吗？我收到此错误：

¨无法将“NSDate”类型的值转换为预期的参数类型“NSDateComponents”¨在线：

错误发生在以下行：

let competitionDay = userCalendar.dateFromComponents(competitionDate)!

这是更完整的代码摘录：

func Date() {               

    // Here we set the current date

    let date = NSDate()
    let calendar = NSCalendar.currentCalendar()
    let components = calendar.components([.Hour, .Minute, .Second, .Nanosecond], fromDate: date)
    let hour = components.hour
    let minutes = components.minute
    let month = components.month
    let year = components.year
    let day = components.day


    let currentDate = calendar.dateFromComponents(components)



    // here we set the due date. When the timer is supposed to finish
    // final Calendar value

        let userCalendar = NSCalendar.currentCalendar()


        let competitionDate:NSDate = myDatePicker.date


        competitionDate.timeIntervalSinceNow


        let competitionDay = userCalendar.dateFromComponents(competitionDate)!


    // Here we compare the two dates
    competitionDay.timeIntervalSinceDate(currentDate!)


    let dayCalendarUnit = calendar.components([NSCalendarUnit.Day, NSCalendarUnit.Hour, NSCalendarUnit.Minute], fromDate: date)


    //here we change the seconds to hours,minutes and days


    let competitionDayDifference = calendar.components([.Day, .Hour, .Minute],
            fromDate: currentDate!, toDate: competitionDay, options: NSCalendarOptions())

    //finally, here we set the variable to our remaining time
    let daysLeft = competitionDayDifference.day
    let hoursLeft = competitionDayDifference.hour
    let minutesLeft = competitionDayDifference.minute

Answer 1

在您最初的问题中，您调用了dateFromComponents，它将NSDateComponents 转换为NSDate，但提供了competitionDate，它已经是NSDate。编译器只是简单地通知你这个错误。

--

顺便说一句，您使用来自NSDate 的.Hour、.Minute、.Second 和.Nanosecond 填充NSDateComponents，然后继续尝试保存对components.year 的引用和components.month 和components.day，即使您没有指定这些组件应包含在NSDateComponents 中。

--

下面你说：

这是一个倒计时应用程序，我让它一直运行，直到我想要一个 DatePicker 来选择我倒计时的日期。比赛日期是截止日期

如果这确实是您想要的，那么可能根本不需要NSDateComponents。我可能只是使用NSDateComponentsFormatter 方法stringFromDate:toDate: 向用户显示两个NSDate 对象之间的时间量的漂亮字符串表示。

例如：

class ViewController: UIViewController {

    @IBOutlet weak var datePicker: UIDatePicker!
    @IBOutlet weak var label: UILabel!

    weak var timer: NSTimer?

    let formatter: NSDateComponentsFormatter = {
        let _formatter = NSDateComponentsFormatter()
        _formatter.allowedUnits = [.Year, .Month, .Day, .Hour, .Minute, .Second]
        _formatter.unitsStyle = .Full

        return _formatter
    }()

    override func viewDidLoad() {
        super.viewDidLoad()

        datePicker.date = NSDate().dateByAddingTimeInterval(1000) // initialize it to whatever you want
    }

    override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)

        timer = NSTimer.scheduledTimerWithTimeInterval(0.1, target: self, selector: "didFireTimer:", userInfo: nil, repeats: true)
    }

    override func viewDidDisappear(animated: Bool) {
        super.viewDidDisappear(animated)

        timer?.invalidate()
    }

    func didFireTimer(timer: NSTimer) {
        label.text = formatter.stringFromDate(NSDate(), toDate: datePicker.date)
    }
}