如何快速获得本周的本周日期

我想要获得周一的本周日期.这在我的表格视图中被视为一周的第一天.
我还需要获得本周的周日.在我的表视图中,这被视为一周的最后一天.

目前的尝试：

let date = NSDate()
let calendar = NSCalendar.currentCalendar()
calendar.firstWeekday = 1
//attempt to changefirstday

let dateFormatter = NSDateFormatter()
let theDateFormat = NSDateFormatterStyle.ShortStyle
let theTimeFormat = NSDateFormatterStyle.ShortStyle
dateFormatter.dateStyle = theDateFormat
dateFormatter.timeStyle = theTimeFormat

let currentDateComponents = calendar.components([.YearForWeekOfYear, .WeekOfYear ], fromDate: date)
let startOfWeek = calendar.dateFromComponents(currentDateComponents)
print("startOfWeek is \(startOfWeek)")
let stringDate = dateFormatter.stringFromDate(startOfWeek!)
print("string date is \(stringDate)") //This is returning Sunday's date

我写了日期扩展以获取特定工作日的日期,这里使用Swift 4是多么容易,

Date.today().next(.monday)                    // Feb 12, 2018 at 12:00 AM
Date.today().next(.sunday)                    //  Feb 11, 2018 at 12:00 AM


Date.today().previous(.sunday)                // Feb 4, 2018 at 12:00 AM
Date.today().previous(.monday)                // Feb 5, 2018 at 12:00 AM

Date.today().previous(.thursday)              // Feb 1, 2018 at 12:00 AM
Date.today().next(.thursday)                  // Feb 15, 2018 at 12:00 AM
Date.today().previous(.thursday,
                      considerToday: true)    // Feb 8, 2018 at 11:04 PM


Date.today().next(.monday)
            .next(.sunday)
            .next(.thursday)                  // Feb 22, 2018 at 12:00 AM

这是Date扩展名,

extension Date {

  static func today() -> Date {
      return Date()
  }

  func next(_ weekday: Weekday, considerToday: Bool = false) -> Date {
    return get(.Next,
               weekday,
               considerToday: considerToday)
  }

  func previous(_ weekday: Weekday, considerToday: Bool = false) -> Date {
    return get(.Previous,
               weekday,
               considerToday: considerToday)
  }

  func get(_ direction: SearchDirection,
           _ weekDay: Weekday,
           considerToday consider: Bool = false) -> Date {

    let dayName = weekDay.rawValue

    let weekdaysName = getWeekDaysInEnglish().map { $0.lowercased() }

    assert(weekdaysName.contains(dayName), "weekday symbol should be in form \(weekdaysName)")

    let searchWeekdayIndex = weekdaysName.index(of: dayName)! + 1

    let calendar = Calendar(identifier: .gregorian)

    if consider && calendar.component(.weekday, from: self) == searchWeekdayIndex {
      return self
    }

    var nextDateComponent = DateComponents()
    nextDateComponent.weekday = searchWeekdayIndex


    let date = calendar.nextDate(after: self,
                                 matching: nextDateComponent,
                                 matchingPolicy: .nextTime,
                                 direction: direction.calendarSearchDirection)

    return date!
  }

}

// MARK: Helper methods
extension Date {
  func getWeekDaysInEnglish() -> [String] {
    var calendar = Calendar(identifier: .gregorian)
    calendar.locale = Locale(identifier: "en_US_POSIX")
    return calendar.weekdaySymbols
  }

  enum Weekday: String {
    case monday, tuesday, wednesday, thursday, friday, saturday, sunday
  }

  enum SearchDirection {
    case Next
    case Previous

    var calendarSearchDirection: Calendar.SearchDirection {
      switch self {
      case .Next:
        return .forward
      case .Previous:
        return .backward
      }
    }
  }
}