获取本月最后一个星期二 ios

Question

可以通过 NSDateComponents 获取当月最后一个工作日吗？例如：一个月的最后一个星期一或一个月的最后一个星期五。等等

Answer 1

只是另一种解决方法。找到下个月的第一天，然后向后搜索星期二。

let calendar = NSCalendar.currentCalendar()
let today = NSDate()
let components = calendar.components([.Year, .Month], fromDate: today)
components.month += 1

// If today is 2016-07-12 then nextMonth will be the 
// first day of the next month: 2016-08-01
if let nextMonth = calendar.dateFromComponents(components) {
    // Search backwards for weekday = Tuesday
    let options: NSCalendarOptions = [.MatchPreviousTimePreservingSmallerUnits, .SearchBackwards]
    calendar.nextDateAfterDate(nextMonth, matchingUnit: .Weekday, value: 3, options: options)
}

Answer 2

这里有一个解决方案；我认为经过测试，并且相当强大。 我们将让 NSCalendar 遍历整个月，一次一天，并提取所有匹配的工作日作为 NSDates。然后您可以回答诸如“本月的第三个星期三”之类的问题

我相信 cmets 很清楚正在发生的事情以及原因。 如果您需要进一步说明，我很乐意这样做。

//What weekday are we interested in? 1 = Sunday . . . 7 = Saturday
NSInteger targetWeekday = 1;

//Using this methodology, GMT timezone is important to set
NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
calendar.timeZone = [NSTimeZone timeZoneWithAbbreviation:@"GMT"];

//set the components to the first of the current month
NSDateComponents *startComponents = [calendar components:NSCalendarUnitMonth | NSCalendarUnitYear fromDate:[NSDate date]];
startComponents.day = 1;

//the enumeration starts "afterDate", so shift the start back one day (86400 seconds) to include the 1st of the month
NSDate *startDate = [[calendar dateFromComponents:startComponents] dateByAddingTimeInterval:-86400];

//the enumeration searches for a match; we'll match at the midnight hour and find every occurance of midnight
NSDateComponents *dayByDay = [[NSDateComponents alloc] init];
dayByDay.hour = 0;

//I've opted to put all matching weekdays of the month into an array, so you can find any instance easily
__block NSMutableArray *foundDates = [NSMutableArray arrayWithCapacity:5];
[calendar enumerateDatesStartingAfterDate:startDate
                       matchingComponents:dayByDay
                                  options:NSCalendarMatchPreviousTimePreservingSmallerUnits
                               usingBlock:^(NSDate *date, BOOL exactMatch, BOOL *stop){
                                   NSDateComponents *thisComponents = [calendar components:NSCalendarUnitMonth | NSCalendarUnitWeekday fromDate:date];
                                   //as long as the month stays the same... (or the year, if you wanted to)
                                   if (thisComponents.month == startComponents.month) {

                                       //does this date match our target weekday search?
                                       if (thisComponents.weekday == targetWeekday) {

                                           //then add it to our result array
                                           [foundDates addObject:date];
                                       }

                                   //once the month has changed, we're done
                                   } else {
                                       *stop = YES;
                                   }
                               }];

//Now, with our search result array, we can find the 1st, last, or any specific occurance of that weekday on that month
NSLog(@"Found these: %@", foundDates);

所以，如果你只想要最后一个，那么只需使用 [foundDates lastObject]

Answer 3

试试这个代码。这对我有用。

NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *comps = [gregorian components:NSWeekdayCalendarUnit fromDate:[NSDate date]];
int weekday = [comps weekday];
int lastTues;
int lastSatDay;
if (weekday==1) {
    lastTues=5;
    lastSatDay=1;
}
else if (weekday==2)
{
    lastTues=6;
    lastSatDay=2;
}
else if (weekday==3)
{
    lastTues=7;
    lastSatDay=3;
}
else if (weekday==4)
{
    lastTues=1;
    lastSatDay=4;
}
else if (weekday==5)
{
    lastTues=2;
    lastSatDay=5;
}
else if (weekday==6)
{
    lastTues=3;
    lastSatDay=6;
}
else if (weekday==7)
{
    lastTues=4;
    lastSatDay=7;
}

NSDate *lastTuesDay = [[NSDate date] addTimeInterval:-3600*24*(lastTues)];
NSDate *lastSaturday = [[NSDate date] addTimeInterval:-3600*24*(lastSatDay)];