How to subtract date components?

Question

As today is Friday, which is 6 according to NSCalendar. I can get this by using the following

Calendar.current.component(.weekday, from: Date())

How do I get weekday component of Saturday last week, which should be 7?

If I do Calendar.current.component(.weekday, from: Date()) - 6 . I am getting 0 which is not valid component.

Answer 1

Try this, you have to get the date first then subtract again from it:

var dayComp = DateComponents(day: -6)
let date = Calendar.current.date(byAdding: dayComp, to: Date())
Calendar.current.component(.weekday, from: date!)

Answer 2

For that first you need to get that date using calendar.date(byAdding:value:to:) and then get day number from it.

extension Date {
    func getDateFor(days:Int) -> Date? {
         return Calendar.current.date(byAdding: .day, value: days, to: Date())
    }
}

Now simply use thus function and get your days.

if let date = Date().getDateFor(days: -6) {
    print(Calendar.current.component(.weekday, from: date))
}