如何在日期ios数组中获取所有星期日

Question

我只想要一个以NSDate的形式包含一年中所有星期一的数组但是很快.我在目标-c中使用以下代码,但不知道如何在swift中使用它.

 NSDate *pickerDate = [NSDate date];
    NSLog(@"pickerDate: %@", pickerDate);

    NSDateComponents *dateComponents;
    NSCalendar *calendar = [NSCalendar currentCalendar];

    dateComponents = [calendar components:NSWeekdayCalendarUnit fromDate:pickerDate];
    NSInteger firstMondayOrdinal = 9 - [dateComponents weekday];
    dateComponents = [[NSDateComponents alloc] init];
    [dateComponents setDay:firstMondayOrdinal];
    NSDate *firstMondayDate = [calendar dateByAddingComponents:dateComponents toDate:pickerDate options:0];

    dateComponents = [[NSDateComponents alloc] init];
    [dateComponents setWeek:1];

    for (int i=0; i<64; i++) {
        [dateComponents setWeek:i];
        NSDate *mondayDate = [calendar dateByAddingComponents:dateComponents toDate:firstMondayDate options:0];
        NSLog(@"week#: %i, mondayDate: %@", i, mondayDate);
    }

Answer 1

Xcode 8或更高版本•Swift 3或更高版本

extension Calendar {
    static let gregorian = Calendar(identifier: .gregorian)
}

extension Date {
    var startOfWeek: Date {
        return Calendar.gregorian.date(from: Calendar.gregorian.dateComponents([.yearForWeekOfYear, .weekOfYear], from: self))!
    }
    var addingOneWeek: Date {
        return Calendar.gregorian.date(byAdding: DateComponents(weekOfYear: 1), to: self)!
    }
    var nextSunday: Date {
        return startOfWeek.addingOneWeek
    }
    func nextFollowingSundays(_ limit: Int) -> [Date] {
        precondition(limit > 0)
        var sundays = [nextSunday]
        sundays.reserveCapacity(limit)
        return [nextSunday] + (0..<limit-1).compactMap { _ in
            guard let next = sundays.last?.addingOneWeek else { return nil }
            sundays.append(next)
            return next
        }
    }
}

用法:

let today = Date()
let nextFollowingSundays = today.nextFollowingSundays(52)
nextFollowingSundays.forEach { sunday in
    print(sunday.description(with: .current), terminator: "\n")
}
// ["Feb 17, 2019 at 12:00 AM", "Feb 24, 2019 at 12:00 AM", "Mar 3, 2019 at 12:00 AM", "Mar 10, 2019 at 12:00 AM", "Mar 17, 2019 at 12:00 AM", "Mar 24, 2019 at 12:00 AM", "Mar 31, 2019 at 12:00 AM", "Apr 7, 2019 at 12:00 AM", "Apr 14, 2019 at 12:00 AM", "Apr 21, 2019 at 12:00 AM", "Apr 28, 2019 at 12:00 AM", "May 5, 2019 at 12:00 AM", "May 12, 2019 at 12:00 AM", "May 19, 2019 at 12:00 AM", "May 26, 2019 at 12:00 AM", "Jun 2, 2019 at 12:00 AM", "Jun 9, 2019 at 12:00 AM", "Jun 16, 2019 at 12:00 AM", "Jun 23, 2019 at 12:00 AM", "Jun 30, 2019 at 12:00 AM", "Jul 7, 2019 at 12:00 AM", "Jul 14, 2019 at 12:00 AM", "Jul 21, 2019 at 12:00 AM", "Jul 28, 2019 at 12:00 AM", "Aug 4, 2019 at 12:00 AM", "Aug 11, 2019 at 12:00 AM", "Aug 18, 2019 at 12:00 AM", "Aug 25, 2019 at 12:00 AM", "Sep 1, 2019 at 12:00 AM", "Sep 8, 2019 at 12:00 AM", "Sep 15, 2019 at 12:00 AM", "Sep 22, 2019 at 12:00 AM", "Sep 29, 2019 at 12:00 AM", "Oct 6, 2019 at 12:00 AM", "Oct 13, 2019 at 12:00 AM", "Oct 20, 2019 at 12:00 AM", "Oct 27, 2019 at 12:00 AM", "Nov 3, 2019 at 1:00 AM", "Nov 10, 2019 at 1:00 AM", "Nov 17, 2019 at 12:00 AM", "Nov 24, 2019 at 12:00 AM", "Dec 1, 2019 at 12:00 AM", "Dec 8, 2019 at 12:00 AM", "Dec 15, 2019 at 12:00 AM", "Dec 22, 2019 at 12:00 AM", "Dec 29, 2019 at 12:00 AM", "Jan 5, 2020 at 12:00 AM", "Jan 12, 2020 at 12:00 AM", "Jan 19, 2020 at 12:00 AM", "Jan 26, 2020 at 12:00 AM", "Feb 2, 2020 at 12:00 AM", "Feb 9, 2020 at 12:00 AM", "Feb 16, 2020 at 12:00 AM"]