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

Question

我们在日历中有这些方便的功能：

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

但我错过了这两个：

• calendar.isDateInNextWeek(日期)

• calendar.isDateInNextMonth(date)

正如@Rob 所提到的，意思是：“在即将到来的星期日开始的日历周中，经过下一个星期六”

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

使用Swift 5和扩展解决的问题Calendar。

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 (sameWeek, nextWeek) 内。

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)

此代码还工作，如果我们想创建DateComponents不当值，就像这样：DateComponents(year: 2019, month: 13)。在这种情况下，它创建 date 01 Jan 2020。

Answer 2

算法不是很壮观：

1. 计算本周的开始
2. 使用 1 的结果来计算下周的开始
3. 使用 2 的结果计算下周后的一周开始
4. 如果日期在下周开始或之后且在下周之后的一周开始之前，则日期在下周

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。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)!

只需切换.CalendarUnitWeekOfMonth，.CalendarUnitMonth您就可以获得本月、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)!

 

和测试：

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 是下周”
“2015-03-22 02:55:19 +0000 是本月”

听起来不错。

如果你想使用<=，==，<等代替难看的（和混淆）NSComparisonResult，你需要这个，以及：

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。如果您想编写适用于旧版本的代码，您必须用dateByAddingUnit:value::toDate:options:旧的 NSDateComponents替换。IE：

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