目标C - 从今天（明天）开始第二天 [英] Objective C - get the following day from today (tomorrow)

问题描述

如何检查日期是否天生就是明天？

How can I check to see if a date is inherently TOMORROW?

我不想在今天这样的日期添加小时或任何东西，因为如果今天已经 22:59 ，添加太多会转到第二天，如果时间 12:00 明天会错过。

I don't want to add hours or anything to a date like today, because if today is already 22:59, adding too much would go over to the day after, and adding too little if the time is 12:00 would miss tomorrow.

如何检查两个 NSDate 并确保一个是等价的明天换另一个？

How can I check two NSDates and ensure that one is the equivalent of tomorrow for the other?

推荐答案

使用 NSDateComponents 您可以提取日/月/ year组件从代表今天的日期开始，忽略小时/分钟/秒组件，添加一天，并重建与明天相对应的日期。

Using NSDateComponents you can extract day/month/year components from the date representing today, ignoring the hour/minutes/seconds components, add one day, and rebuild a date corresponding to tomorrow.

所以想象你想要恰好在当前日期添加一天（包括保持小时/分钟/秒inf ormation与now日期相同），你可以使用 dateWithTimeIntervalSinceNow 将timeInterval 24 * 60 * 60秒添加到now，但它更好（和DST一样） -proof etc）使用 NSDateComponents 这样做：

So imagine you want to add exactly one day to the current date (including keeping hours/minutes/seconds information the same as the "now" date), you could add a timeInterval of 24*60*60 seconds to "now" using dateWithTimeIntervalSinceNow, but it is better (and DST-proof etc) to do it this way using NSDateComponents:

NSDateComponents* deltaComps = [[[NSDateComponents alloc] init] autorelease];
[deltaComps setDay:1];
NSDate* tomorrow = [[NSCalendar currentCalendar] dateByAddingComponents:deltaComps toDate:[NSDate date] options:0];

但如果你想生成明天午夜对应的日期，您可以只检索现在代表的日期的月/日/年组件，不带小时/分/秒零件，然后再添加1天，然后重建日期：

But if you want to generate the date corresponding to tomorrow at midnight, you could instead just retrieve the month/day/year components of the date representing now, without hours/min/secs part, and add 1 day, then rebuild a date:

// Decompose the date corresponding to "now" into Year+Month+Day components
NSUInteger units = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay;
NSDateComponents *comps = [[NSCalendar currentCalendar] components:units fromDate:[NSDate date]];
// Add one day
comps.day = comps.day + 1; // no worries: even if it is the end of the month it will wrap to the next month, see doc
// Recompose a new date, without any time information (so this will be at midnight)
NSDate *tomorrowMidnight = [[NSCalendar currentCalendar] dateFromComponents:comps];

PS：您可以在日期和时间编程指南，尤其是这里关于日期组件。

P.S.: You can read really useful advice and stuff about date concepts in the Date and Time Programming Guide, especially here about date components.

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