Xcode - 设置月份中的星期，然后获取一年中的一周

Question

当前尝试使用NSDateFormatter和NSDateComponents来设置一个月的周数，然后找到一年中的哪一周。

假设我们有一个日期：20/05/2020，然后将周数设置为 0、1 或 2 等，然后从中找出一年中的一周。

到目前为止，我已经尝试过使用NSDateComponents：

NSDate *date = self.date; // 20/05/2020
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *components = [calendar components:NSCalendarUnitMonth | NSCalendarUnitYear fromDate:date];
[components setWeekOfMonth:1];
NSDate *newDate = [calendar dateFromComponents:components];
NSInteger weekOfYear = [calendar components:NSCalendarUnitWeekOfYear fromDate:newDate].weekOfYear;

我总是得到输出18.

预期产出：

Change week of month to: 1 | output: 19 (4th)
Change week of month to: 2 | output: 20 (11th)
Change week of month to: 3 | output: 21 (18th)
Change week of month to: 4 | output: 22 (25th)

Answer 1

问题是在日期组件中设置setWeekOfMonth不起作用。

而是设置weekday和weekdayOrdinal

NSDate *date = self.date; // 20/05/2020
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *components = [calendar components:NSCalendarUnitMonth | NSCalendarUnitYear fromDate:date];
components.weekday = 2;
components.weekdayOrdinal = 3;
NSDate *newDate = [calendar dateFromComponents:components];
NSInteger weekOfYear = [calendar components:NSCalendarUnitWeekOfYear fromDate:newDate].weekOfYear;

---

这是一种不同的方法：

它计算当月的第一个星期一，然后枚举下一个星期一，直到月底。

- (NSArray *)yearOfWeeksInCurrentMonth
{
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *components = [calendar components: NSCalendarUnitMonth | NSCalendarUnitYear fromDate:[NSDate date]];
components.weekday = 2;
components.weekdayOrdinal = 1;
NSDate *firstMonday = [calendar dateFromComponents:components];
NSInteger weekOfYear = [calendar component:NSCalendarUnitWeekOfYear fromDate:firstMonday];
__block NSMutableArray *result = [NSMutableArray array];
[result addObject:@[firstMonday, @(weekOfYear)]];
NSDateComponents *weekComponents = [calendar components: NSCalendarUnitWeekday fromDate:firstMonday];
[calendar enumerateDatesStartingAfterDate:firstMonday matchingComponents:weekComponents options:NSCalendarMatchNextTime usingBlock:^(NSDate * _Nullable date, BOOL exactMatch, BOOL * _Nonnull stop) {
if (date != nil) {
if ( [calendar component:NSCalendarUnitMonth fromDate:date] > components.month ) {
*stop = YES;
} else {
NSInteger weekOfYear = [calendar component:NSCalendarUnitWeekOfYear fromDate:date];
[result addObject:@[date, @(weekOfYear)]];
}
}
}];
return [result copy];
}

返回值是一个数组，其中包含日期 (NSDate( 和相应的年份周 (NSNumber(

(
(
"2020-05-03 22:00:00 +0000",
19
),
(
"2020-05-10 22:00:00 +0000",
20
),
(
"2020-05-17 22:00:00 +0000",
21
),
(
"2020-05-24 22:00:00 +0000",
22
)
)