如何在iPhone sdk中获取当前日期的下一个和更早的日期 [英] How do I get the next and earlier date of the current date in iPhone sdk

问题描述

我有一个约会对象，

NSDate * date = [NSDate date];

NSDate *date = [NSDate date];

现在我想要在此日期之前和之后的日期。我应该使用什么功能。

Now I want a date earlier of this date and next of it. What function should I use.

早期和晚期是指前一天和后一天。

Earlier and Later means a day before and a day after.

我也是尝试使用earlyDate，但可能是我使用它错了，因为它返回相同的日期。

Also I tried using earlierDate but may be I am using it wrong since it is returning the same date.

tnx。

推荐答案

NSDate有点用词不当。这不是一个简单的日期，它是一个时间日期，具有亚秒级精度。 earlyDate：方法是一个比较函数，它返回两个日期中较早的日期，它不会创建较早的日期。如果您关心的是您当前所关注的日期，则可以执行以下操作：

NSDate is a bit of a misnomer. It is a not a simple date, it is a date a time, with subsecond level precision. The earlierDate: method is a comparison function that returns which ever of the two dates is earlier, it does not create an earlier date. If all you care about is a date that is before your current one you can do:

NSDate *earlierDate = [date addTimeInterval:-1.0];

这将在日期前1秒返回日期。同样你可以做到

Which will return a date 1 second before date. Likewise you can do

NSDate *laterDate = [date addTimeInterval:1.0];

未来1秒的日期。

如果您想要提前一天，可以添加几天的秒数。当然这是近似的，除非你处理所有格里历日历问题，但如果你只想快速近似：

If you want a day earlier you can add a days worth of seconds. Of course that is approximate unless you deal with all the gregorian calendar issues, but if you just want a quick approximation:

NSDate *earlierDate = [date addTimeInterval:(-1.0*24*60*60)];

这不适用于闰秒等，但对于大多数用途来说它可能没问题。

That doesn't work with leap seconds, etc, but for most uses it is probably fine.

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