一年中两个NSDates之间的天数很快

时间:2015-06-30 07:30:02

标签: ios xcode swift date nsdate

我正在构建生日提醒应用。我希望用户能够看到有多少天,直到有人的下一个生日。

我们说我有NSDate() = 2015-06-30 07:21:47 +0000

生日的NSDate = 1985-08-29 12:00:00 +0000

我如何获得下一个生日的天数?我使用了this之类的东西,它给出了自日期实际开始以来的负天数(在出生日期中有数千天)。然后,我将添加365数字差异,直到它是积极的,但它仍然返回一个不稳定的数字。我假设是因为闰年或其他事情。

我能实施一种方法吗?以某种方式平衡年份组成部分,以便它始终比较下一个生日而不是原始生日?

编辑:

这是我正在使用的功能:

func daysBetween(date1: NSDate, date2: NSDate) -> Int {

    var calendar: NSCalendar = NSCalendar.currentCalendar()

    let date1 = calendar.startOfDayForDate(date1)
    let date2 = calendar.startOfDayForDate(date2)

    let flags = NSCalendarUnit.CalendarUnitDay
    let components = calendar.components(flags, fromDate: date1, toDate: date2, options: nil)

    return components.day
}

根据我发布的示例日期,我会像这样使用它:

// sampleDate = 1985-08-29 12:00:00 +0000
daysBetween(sampleDate, date2: NSDate())
// --> 10897

无论是正面还是负面,这个数字都是数千。我希望将其平衡到下一个日历生日的天数。

2 个答案:

答案 0 :(得分:8)

您需要的是计算(日和月)的下一次出现 今天过后生日的一部分:

let cal = NSCalendar.currentCalendar()
let today = cal.startOfDayForDate(NSDate())
let dayAndMonth = cal.components(.CalendarUnitDay | .CalendarUnitMonth,
    fromDate: birthday)
let nextBirthDay = cal.nextDateAfterDate(today,
    matchingComponents: dayAndMonth,
    options: .MatchNextTimePreservingSmallerUnits)!

说明:

  • MatchNextTimePreservingSmallerUnits选项的目的是 如果生日是在2月29日(在公历中),它的下一次出现将是 如果年份不是闰年,则计算为3月1日。

  • 您可能需要先检查生日是今天,看起来如此 在这种情况下,nextDateAfterDate()将返回下一个生日。

然后您可以像往常一样计算天数差异:

let diff = cal.components(.CalendarUnitDay,
    fromDate: today,
    toDate: nextBirthDay,
    options: nil)
println(diff.day)

更新Swift 2.2(Xcode 7.3):

let cal = NSCalendar.currentCalendar()
let today = cal.startOfDayForDate(NSDate())
let dayAndMonth = cal.components([.Day, .Month],
                                 fromDate: birthday)
let nextBirthDay = cal.nextDateAfterDate(today,
                                         matchingComponents: dayAndMonth,
                                         options: .MatchNextTimePreservingSmallerUnits)!

let diff = cal.components(.Day,
                          fromDate: today,
                          toDate: nextBirthDay,
                          options: [])
print(diff.day)

更新Swift 3(Xcode 8 GM):

let cal = Calendar.current
let today = cal.startOfDay(for: Date())
let dayAndMonth = cal.dateComponents([.day, .month], from: birthday)
let nextBirthDay = cal.nextDate(after: today, matching: dayAndMonth,
                                matchingPolicy: .nextTimePreservingSmallerComponents)!

let diff = cal.dateComponents([.day], from: today, to: nextBirthDay)
print(diff.day!)

答案 1 :(得分:4)

顺便说一下,如果有人需要这里是Swift 3中的@Aaron函数:

func daysBetween(date1: Date, date2: Date) -> Int {
    let calendar = Calendar.current

    let date1 = calendar.startOfDay(for: date1)
    let date2 = calendar.startOfDay(for: date2)

    let components = calendar.dateComponents([Calendar.Component.day], from: date1, to: date2)

    return components.day ?? 0
}