Swift - Start day and end day of the week before previous week - swift

Question

Today is Friday 6 March. How to find that 16 Feb is the start day and 22 Feb is the end day of the week before previous week.
16 is for my country Bulgaria in USA will be 15 and 21 I use .currentCalendar()

Answer 1

Something like this should work:
let cal = NSCalendar.currentCalendar()
let components = NSDateComponents()
components.weekOfYear -= 1
if let date = cal.dateByAddingComponents(components, toDate: NSDate(), options: NSCalendarOptions(0)) {
var beginningOfWeek: NSDate?
var weekDuration = NSTimeInterval()
if cal.rangeOfUnit(.CalendarUnitWeekOfYear, startDate: &beginningOfWeek, interval: &weekDuration, forDate: date) {
let endOfWeek = beginningOfWeek?.dateByAddingTimeInterval(weekDuration)
print(beginningOfWeek) // Optional(2015-02-15 05:00:00 +0000)
print(endOfWeek) // Optional(2015-02-22 05:00:00 +0000)
}
}

Answer 2

A simpler Swift 2 alternative as an extension, derived from Martin R's answer for getting the end of the month:
extension: NSDate {
func startOfWeek(weekday: Int?) -> NSDate? {
guard
let cal: NSCalendar = NSCalendar.currentCalendar(),
let comp: NSDateComponents = cal.components([.YearForWeekOfYear, .WeekOfYear], fromDate: self) else { return nil }
comp.to12pm()
cal.firstWeekday = weekday ?? 1
return cal.dateFromComponents(comp)!
}
func endOfWeek(weekday: Int) -> NSDate? {
guard
let cal: NSCalendar = NSCalendar.currentCalendar(),
let comp: NSDateComponents = cal.components([.WeekOfYear], fromDate: self) else { return nil }
comp.weekOfYear = 1
comp.day -= 1
comp.to12pm()
return cal.dateByAddingComponents(comp, toDate: self.startOfWeek(weekday)!, options: [])!
}
}
Usage:
// Use 2 for Monday, 1 for Sunday:
print(NSDate().startOfWeek(1)!) // "2016-01-24 08:00:00 +0000\n"
print(NSDate().endOfWeek(1)!) // "2016-01-30 08:00:00 +0000\n"
To guard against DST and such, you should also implement an extension to force the time to 12 pm:
internal extension NSDateComponents {
func to12pm() {
self.hour = 12
self.minute = 0
self.second = 0
}
}

Answer 3

If anyone looking for swift 3 answer:
func startOfWeek(weekday: Int?) -> Date {
var cal = Calendar.current
var component = cal.dateComponents([.yearForWeekOfYear, .weekOfYear], from: self)
component.to12am()
cal.firstWeekday = weekday ?? 1
return cal.date(from: component)!
}
func endOfWeek(weekday: Int) -> Date {
let cal = Calendar.current
var component = DateComponents()
component.weekOfYear = 1
component.day = -1
component.to12pm()
return cal.date(byAdding: component, to: startOfWeek(weekday: weekday))!
}
I set to 00:00:00 of that day
internal extension DateComponents {
mutating func to12am() {
self.hour = 0
self.minute = 0
self.second = 0
}
mutating func to12pm(){
self.hour = 23
self.minute = 59
self.second = 59
}
}

Answer 4

Swift 4+:
A very straightforward approach using mainly Calendar with the help of DateComponents:
Get Date
Go to previous week
Calendar.current.date(byAdding: .weekdayOrdinal, value: -1, to: aDate)
Get the current weekday
Calendar.current.component(.weekday, from: bDate)
Compute an offset from this weekday
Negative offset to reach the start of week
Positive offset to the reach end of the week
Use offset to go to the required date
Calendar.current.date(byAdding: .day, value: offset, to: bDate)
Solution:
extension Date {
var firstWeekdayOfLastWeek: Date? {
guard let previousWeek = Calendar.current.date(byAdding: .weekdayOrdinal,
value: -1, to: self)
else { return nil }
let offsetToFirstWeekday: Int = {
let currentWeekday = Calendar.current.component(.weekday, from: previousWeek)
guard currentWeekday > 0 else { return 0 }
return 1 - currentWeekday
}()
let result = Calendar.current.date(byAdding: .day,
value: offsetToFirstWeekday,
to: previousWeek)
return result
}
var lastWeekdayOfLastWeek: Date? {
guard let previousWeek = Calendar.current.date(byAdding: .weekdayOrdinal,
value: -1, to: self)
else { return nil }
let offsetToLastWeekday: Int = {
let currentWeekday = Calendar.current.component(.weekday, from: previousWeek)
return 7 - currentWeekday
}()
let result = Calendar.current.date(byAdding: .day,
value: offsetToLastWeekday,
to: previousWeek)
return result
}
}
Usage Example:
let formatter = DateFormatter()
formatter.dateStyle = .long
let date = Date()
//My current system date (as of time of writing)
print(formatter.string(from: currentDate)) //December 11, 2020
//Results (my system has Sunday as the start of the week)
print(formatter.string(from: date.firstWeekdayOfLastWeek!)) //November 29, 2020
print(formatter.string(from: date.lastWeekdayOfLastWeek!)) //December 5, 2020
Force unwrap is for example purposes only