Question

快速计算到另一个日期的天数，小时数，分钟数和秒数。

我已经尝试过在函数中使用swifts datecomponents，但是它为我返回的天数不正确。

@objc func createCountdown(){
    let date = Date()
    let calendar = Calendar.current

    let components = calendar.dateComponents([.day, .hour, .minute, .second], from: date)

    let currentDate = calendar.date(from: components)

    let userCalendar = Calendar.current

    var birthdayDate = DateComponents()
    //Get user's birthday
    birthdayDate.month = 4
    birthdayDate.day = 16
    birthdayDate.hour = 0
    birthdayDate.minute = 0


    let birthday = userCalendar.date(from: birthdayDate as DateComponents)


    let BirthdayDifference = calendar.dateComponents([.day, .hour, .minute, .second], from: currentDate!, to: birthday!)

    let daysLeft = BirthdayDifference.day
    let hoursLeft = BirthdayDifference.hour
    let minutesLeft = BirthdayDifference.minute
    let secondsLeft = BirthdayDifference.second

    daysLabel.text = String(daysLeft!)
    hoursLabel.text = String(hoursLeft!)
    minutesLabel.text = String(minutesLeft!)
    secondsLabel.text = String(secondsLeft!)
}

代码中的测试日期为生日值。我只是想从当前日期开始将天，小时，分钟和秒倒数到指定的生日。

此输出为74天，但显然今天从2018年12月31日到2019年4月16日超过74天。那是大约105天，而不是74天。任何建议都将不胜感激。

谢谢。

Answer 1

您需要根据生日那天和月份找出下一个生日。您可以使用日历的方法nextDate(after: Date, matching: DateComponents)

func nextDate(after date: Date, matching components: DateComponents, matchingPolicy: Calendar.MatchingPolicy, repeatedTimePolicy: Calendar.RepeatedTimePolicy = default, direction: Calendar.SearchDirection = default) -> Date?

let birthDateCoponents = DateComponents(month: 4, day: 16)
let nextBirthDate = Calendar.current.nextDate(after: Date(), matching: birthDateCoponents, matchingPolicy: .nextTime)!

let difference = Calendar.current.dateComponents([.day, .hour, .minute, .second], from: Date(), to: nextBirthDate)

difference.day     // 105
difference.hour    // 2
difference.minute  // 5
difference.second  // 30

向用户显示它时，可以将DateComponentsFormatter与相应的unitsStyle一起使用。您可以在下面看到使用.full样式并将单位限制为.day, .hour, .minute, .second时的外观：

let formatter = DateComponentsFormatter()
formatter.allowedUnits = [.day, .hour, .minute, .second]

formatter.unitsStyle = .full
formatter.string(from: Date(), to: nextBirthDate)  // "105 days, 1 hour, 44 minutes, 36 seconds"

如何快速计算从现在到特定日期的天，小时，分钟

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