Exclude dates from date calculation

Question

I'm looking to calculate the time in between 2 dates. I've been using DateComponentsFormatter, which works great for outputting properly in all languages/regions/calendars.

I'd like to add the ability to exclude weekends from this calculation. It doesn't seem to support this natively. Is there a good alternative (native or 3rd party libraries) to remove a set of dates from the calculation?

Answer 1

You can perform this type of calculation natively using the Calendar API; you're just going to have to write it manually:

import Foundation

// The nextWeekend API is available only on 10.12 or later.
if #available(OSX 10.12, *) {

let calendar = Calendar(identifier: .gregorian)
let start = calendar.date(from: DateComponents(year: 2018, month: 3, day: 18))!
let end   = calendar.date(from: DateComponents(year: 2018, month: 4, day: 7))!

var total: TimeInterval = 0

// We'll iterate weekends from now until the target end date,
// adding the intervening time from during the week.
var current = start
while current < end {
    guard let weekend = calendar.nextWeekend(startingAfter: current) else {
        break
    }

    if weekend.start > end {
        // Our target end date is before the next weekend; add whatever time is left.
        total += end.timeIntervalSince(current)
        break
    } else {
        // There's >= 1 weekend between now and the target date; add the week in between.
        total += weekend.start.timeIntervalSince(current)
        current = weekend.end
    }
}

let formatter = DateComponentsFormatter()
formatter.allowedUnits = .day
print(formatter.string(from: total)!) // => 16d

}