Swift

Question

我们在日历中有那些方便的功能：

let calendar = NSCalendar.currentCalendar()
calendar.isDateInToday(date)
calendar.isDateInTomorrow(date)

但我错过了那两个：

calendar.isDateInNextWeek(日期)
calendar.isDateInNextMonth(日期)

正如@Rob所说，意思是："in the calendar week starting this coming Sunday, going through the following Saturday"

我很难弄清楚如何以涵盖所有极端情况的稳健方式实现这些功能。

有人可以提供助手吗？

Answer 1

我想出了这个天真的代码：

extension NSCalendar
{
    func isDateInNextWeek(value: NSDate) -> Bool
    {
        let componentsValue = self.components(.WeekOfYearCalendarUnit | .YearCalendarUnit,  fromDate: value)
        let componentsToday = self.components(.WeekOfYearCalendarUnit | .YearCalendarUnit,  fromDate: NSDate())

        let weekOfYearValue = componentsValue.weekOfYear
        let weekOfYearToday = componentsToday.weekOfYear
        let yearValue = componentsValue.year
        let yearToday = componentsToday.year

        if(yearValue < yearToday)
        {
            return false
        }
        else if(yearValue == yearToday && weekOfYearValue - weekOfYearToday == 1)
        {
           return true
        }
        else if(yearValue - yearToday == 1 && weekOfYearValue == 1 && weekOfYearToday == 52)
        {
            return true
        }
        else
        {
            return false
        }
    }
}

但我一定遗漏了一些边缘情况。

Answer 2

算法不是很壮观：

计算本周的开始
使用 1 的结果计算下周的开始
使用 2 的结果计算下周之后的一周开始时间
如果日期在下周开始日或之后，并且在下周之后的一周开始之前，则为下周

NSCalendar 为我们完成了大部分工作。但它看起来还是有点吓人，至少如果你不经常使用这些日期方法的话。您应该阅读所有这些方法的文档以了解它们。

let calendar = NSCalendar.currentCalendar()
let date = NSDate()

var startOfThisWeek: NSDate?
if !calendar.rangeOfUnit(.CalendarUnitWeekOfMonth, startDate: &startOfThisWeek, interval: nil, forDate: date) {
    fatalError("Can't calculate start of this week")
}
let startOfNextWeek = calendar.dateByAddingUnit(.CalendarUnitWeekOfMonth, value: 1, toDate: startOfThisWeek!, options: nil)!
let startOfNextNextWeek = calendar.dateByAddingUnit(.CalendarUnitWeekOfMonth, value: 1, toDate: startOfNextWeek, options: nil)!

只需将 .CalendarUnitWeekOfMonth 切换为 .CalendarUnitMonth 即可获得本月、下个月和下个月的计算结果。

var startOfThisMonth: NSDate?
if !calendar.rangeOfUnit(.CalendarUnitMonth, startDate: &startOfThisMonth, interval: nil, forDate: date) {
    fatalError("Can't calculate start of this month")
}
let startOfNextMonth = calendar.dateByAddingUnit(.CalendarUnitMonth, value: 1, toDate: startOfThisMonth!, options: nil)!
let startOfNextNextMonth = calendar.dateByAddingUnit(.CalendarUnitMonth, value: 1, toDate: startOfNextMonth, options: nil)!

测试：

let testDate = NSDate(timeIntervalSinceNow: 7*24*60*60)

if startOfThisWeek <= testDate && testDate < startOfNextWeek {
    println("\(testDate) is this week")
}
if startOfNextWeek <= testDate && testDate < startOfNextNextWeek {
    println("\(testDate) is next week")
}
if startOfThisMonth <= testDate && testDate < startOfNextMonth {
    println("\(testDate) is this month")
}
if startOfNextMonth <= testDate && testDate < startOfNextNextMonth {
    println("\(testDate) is next month")
}

结果：

"2015-03-22 02:55:19 +0000 is next week"
"2015-03-22 02:55:19 +0000 is this month"

听起来不错。

如果你想使用 <=、==、< 等而不是丑陋的（和令人困惑的）NSComparisonResult，你也需要这个：

public func ==(lhs: NSDate, rhs: NSDate) -> Bool {
    return lhs === rhs || lhs.compare(rhs) == .OrderedSame
}

public func <(lhs: NSDate, rhs: NSDate) -> Bool {
    return lhs.compare(rhs) == .OrderedAscending
}

extension NSDate: Comparable { }

这是 iOS8 代码。如果你想编写适用于旧版本的代码，你必须将 dateByAddingUnit:value::toDate:options: 替换为良好的旧 NSDateComponents。即：

let offSetComponents = NSDateComponents()
offSetComponents.weekOfMonth = 1
let startOfNextWeek = calendar.dateByAddingComponents(offSetComponents, toDate: startOfThisWeek, options: nil)

Answer 3

使用 Swift 5 和扩展 Calendar 解决了问题。

extension Calendar {
  private var currentDate: Date { return Date() }

  func isDateInThisWeek(_ date: Date) -> Bool {
    return isDate(date, equalTo: currentDate, toGranularity: .weekOfYear)
  }

  func isDateInThisMonth(_ date: Date) -> Bool {
    return isDate(date, equalTo: currentDate, toGranularity: .month)
  }

  func isDateInNextWeek(_ date: Date) -> Bool {
    guard let nextWeek = self.date(byAdding: DateComponents(weekOfYear: 1), to: currentDate) else {
      return false
    }
    return isDate(date, equalTo: nextWeek, toGranularity: .weekOfYear)
  }

  func isDateInNextMonth(_ date: Date) -> Bool {
    guard let nextMonth = self.date(byAdding: DateComponents(month: 1), to: currentDate) else {
      return false
    }
    return isDate(date, equalTo: nextMonth, toGranularity: .month)
  }

  func isDateInFollowingMonth(_ date: Date) -> Bool {
    guard let followingMonth = self.date(byAdding: DateComponents(month: 2), to: currentDate) else {
      return false
    }
    return isDate(date, equalTo: followingMonth, toGranularity: .month)
  }
}

用法：

let day: Double = 60 * 60 * 24
let currentDate = Date() // Thu 25 Apr 2019
let futureDate = Date(timeInterval: 3 * day, since: currentDate) // Sun 28 Apr 2019
if Calendar.current.isDateInThisWeek(futureDate) { 
    // this will be executed if first day of week is Monday
} else {
    // this will be executed if first day of week is Sunday
}

代码根据 Calendar 实例评估日期是否在范围内（sameWeek，nextWeek）。

如果 Calendar 实例是 current 它将根据设备设置确定一周的开始（星期一或星期日），但如果您想要不同的行为，您可以更改 Calendar 实例: Calendar(identifier: .chinese).isDateInNextWeek(someDate)

如果我们尝试使用不正确的值创建 DateComponents，此代码也有效，例如：DateComponents(year: 2019, month: 13)。在这种情况下，它创建日期 01 Jan 2020.

Swift - 检查日期是否在下周/下月。 ( isDateInNextWeek() isDateInNextMonth() )

Swift - Check if date is in next week / month. ( isDateInNextWeek() isDateInNextMonth() )

xcode

nsdate

nscalendar