雨燕4.2

Question

我想要获得本周的第一天（比如本周，我应该会在2015-09-13获得）。

但是我在Apple提供的源代码中找不到合适的功能。

代码应该是这样的......

print(getFirstDay(40)) // Should print 27

func getFirstDay(weekNumber:Int)->Int?{
    let formatter = NSDateFormatter()
    formatter.dateFormat = "yyyy-MM-dd"
    if let todayDate = formatter.dateFromString(weekNumber) {
        let myCalendar = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian)!
        let myComponents = myCalendar.dateFromComponents(.weekOfYear)
        let date = myComponents.date
        return date
    } else {
        return nil
    }
}

然而，上面的代码并没有起作用（显然），但我认为这应该是正确的方向。

我怎样才能实现这个目标？

/ *不重要* / 我正在尝试在表格视图中创建一种日历应用程序，该视图由4周的章节分隔，我想知道新周开始的日期。

Answer 1

经过一些试验和错误，如果您使用的是Swift3 + iOS10，这是正确的解决方案。这将计算Dec / Jan跨越边界的正确日期。

    extension Date {
        var components:DateComponents {
            let cal = NSCalendar.current
            return cal.dateComponents(Set([.year, .month, .day, .hour, .minute, .second, .weekday, .weekOfYear, .yearForWeekOfYear]), from: self)
        }
    }

    private static func getWeekFirstDay(from sourceDate:Date) -> Date? {
        let Calendar = NSCalendar(calendarIdentifier: .gregorian)!
        var sourceComp = sourceDate.components
        var comp = DateComponents()
        comp.weekOfYear = sourceComp.weekOfYear
        comp.weekday = 1
        comp.yearForWeekOfYear = sourceComp.yearForWeekOfYear
        return Calendar.date(from: comp)
    }

Answer 2

    func getFirstDay(weekNumber:Int)->String?{
        let Calendar = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian)!
        let dayComponent = NSDateComponents()
        dayComponent.weekOfYear = weekNumber
        dayComponent.weekday = 1
        dayComponent.year = 2015
        var date = Calendar.dateFromComponents(dayComponent)

        if(weekNumber == 1 && Calendar.components(.Month, fromDate: date!).month != 1){
            print(Calendar.components(.Month, fromDate: date!).month)
            dayComponent.year = 2014
            date = Calendar.dateFromComponents(dayComponent)
        }
        let dateFormatter = NSDateFormatter()
        dateFormatter.dateFormat = "dd-MM-yyyy"
        return String(dateFormatter.stringFromDate(date!))
    }

到目前为止我做的非常粗糙的代码。

它适用于查找一周的第一天;）！

Answer 3

let calendar = NSCalendar.currentCalendar()
let components = calendar.components(.CalendarUnitYear | .CalendarUnitWeekOfYear | .CalendarUnitWeekday, fromDate: NSDate())

components.calendar = calendar

components.weekday = 2 // 2 = Monday
components.weekOfYear = 39

let firstDayOfWeek = components.date

这将为您提供当年第39周的星期一日期。

Answer 4

雨燕4.2

更多通用解决方案

func getFirstDay(WeekNumber weekNumber:Int, CurrentYear currentYear: Int)->String?{
    let Calendar = NSCalendar(calendarIdentifier: .gregorian)!
    var dayComponent = DateComponents()
    dayComponent.weekOfYear = weekNumber
    dayComponent.weekday = 1
    dayComponent.year = currentYear
    var date = Calendar.date(from: dayComponent)

    if(weekNumber == 1 && Calendar.components(.month, from: date!).month != 1){
        //print(Calendar.components(.month, from: date!).month)
        dayComponent.year = currentYear - 1
        date = Calendar.date(from: dayComponent)
    }
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "yyyy/MM/dd"
    return String(dateFormatter.string(from: date!))
}

Answer 5

我的Xcode 12和Swift 5解决方案

extension Date {

   var year: Int? {
       var calendar = Calendar.current
       let currentComponents = calendar.dateComponents([.year], from: self)
       return currentComponents.year
   }
} 

class func getWeekOfYear(from week: Int, year: Int? = Date().year, locale: Locale? = nil) -> Date? {
        var calendar = Calendar.current
        calendar.locale = locale
        let dateComponents = DateComponents(calendar: calendar, year: year, weekday: 1, weekOfYear: week)
        return calendar.date(from: dateComponents)
    }

您可以通过以下方式运行它：

  getWeekOfYear(from: 38)             // Optional(2020-09-13 22:00:00 +0000)
  getWeekOfYear(from: 38, year: 2020) // Optional(2020-09-13 22:00:00 +0000)
  getWeekOfYear(from: 38, year: 2020, locale: Locale(identifier: de_DE) ) // Optional(2020-09-13 22:00:00 +0000)

插件：

extension Date {

   func isBetween(_ date1: Date, and date2: Date) -> Bool {
      return (min(date1, date2) ... max(date1, date2)).contains(self)
   }

   var startOfWeek: Date? {
      var calendar = Calendar.current
      return calendar.dateInterval(of: .weekOfMonth, for: self)?.start
   }

   var endOfWeek: Date? {
       var calendar = Calendar.current
       return calendar.dateInterval(of: .weekOfMonth, for: self)?.end
   }

   var startOfMonth: Date? {
       var calendar = Calendar.current
       return calendar.dateInterval(of: .month, for: self)?.start
   }

   var endOfMonth: Date? {
       var calendar = Calendar.current
       return calendar.dateInterval(of: .month, for: self)?.end
   }

   var weekNumber: Int? {
       var calendar = Calendar.current
       let currentComponents = calendar.dateComponents([.weekOfYear], from: self)
       return currentComponents.weekOfYear
   }

   var monthNumber: Int? {
       var calendar = Calendar.current
       let currentComponents = calendar.dateComponents([.month], from: self)
       return currentComponents.month
   }
}

您可以通过以下方式运行它：

let date = Date() // Optional(2020-09-13 22:00:00 +0000)
date.monthNumber  // Optional(9)
date.weekNumber   // Optional(38)

...

使用Swift中的Weeknumber获取一周的第一天

5 个答案:

雨燕4.2