如何在 Objective-C 中的特殊日期获得一周中的星期一?
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【中文标题】如何在 Objective-C 中的特殊日期获得一周中的星期一?【英文标题】:How can I get the monday of a week in a special date in Objective-C? 【发布时间】:2010-10-08 13:40:43 【问题描述】:例如01.10.2010 是星期五 => 27.09.2010 是星期一。
我不知道如何管理这个。顺便说一句:我如何计算日期?
【问题讨论】:
【参考方案1】:对于time/date calculations,使用 NSDateComponents。
清单 2 获取本周的星期日
NSDate *today = [[NSDate alloc] init];
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
// Get the weekday component of the current date
NSDateComponents *weekdayComponents = [gregorian components:NSWeekdayCalendarUnit fromDate:today];
/*
Create a date components to represent the number of days to subtract from the current date.
The weekday value for Sunday in the Gregorian calendar is 1, so subtract 1 from the number of days to subtract from the date in question. (If today's Sunday, subtract 0 days.)
*/
NSDateComponents *componentsToSubtract = [[NSDateComponents alloc] init];
[componentsToSubtract setDay: 0 - ([weekdayComponents weekday] - 1)];
NSDate *beginningOfWeek = [gregorian dateByAddingComponents:componentsToSubtract toDate:today options:0];
/*
Optional step:
beginningOfWeek now has the same hour, minute, and second as the original date (today).
To normalize to midnight, extract the year, month, and day components and create a new date from those components.
*/
NSDateComponents *components =
[gregorian components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit)
fromDate: beginningOfWeek];
beginningOfWeek = [gregorian dateFromComponents:components];
在以后的版本中,有更聪明的办法:
NSCalendar *cal = [NSCalendar currentCalendar];
[cal setFirstWeekday:2]; //2 is monday. 1:Sunday .. 7:Saturday don't set it, if user's locale should determine the start of a week
NSDate *now = [NSDate date];
NSDate *monday;
[cal rangeOfUnit:NSWeekCalendarUnit // we want to have the start of the week
startDate:&monday // we will write the date object to monday
interval:NULL // we don't care for the seconds a week has
forDate:now]; // we want the monday of today's week
如果您确实更改了表示一周开始的工作日(星期日与星期一),则应在此 sn-p 之后将其更改回来。
【讨论】:
看起来很复杂 :> 。但这是一个很好的例子。谢谢以上是关于如何在 Objective-C 中的特殊日期获得一周中的星期一?的主要内容,如果未能解决你的问题,请参考以下文章
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