在iPhone上两个NSDates之间循环的最简单的方法？ [英] Simplest way to loop between two NSDates on iPhone?

问题描述

从一个日期循环到另一个日期的最简单的方法是什么？

What's the simplest way to loop from one date to another?

我想要的概念是这样的：

What I want conceptually is something like this:

for (NSDate *date = [[startDate copy] autorelease]; [date compare: endDate] < 0;
     date = [date dateByAddingDays: 1]) {
    // do stuff here
}

当然：没有 dateByAddingDays：。

这是我想到的：

• 我不能只添加一个 NSTimeInterval ，因为一天中的秒数可能不同。 li>
  
• 我可以将其分解为 NSDateComponents ，并向组件添加一天，然后重新组装。但是这是冗长而又丑陋的代码。

• I can't just add an NSTimeInterval, since the number of seconds in a day can vary.
• I could break it down into NSDateComponents and add one day to the components, then reassemble it. But that's long and ugly code.

所以我希望有人尝试了几个选项，找到了一个好的。任何想法？

So I'm hoping someone has tried a few options for this, and found a good one. Any ideas?

推荐答案

为DateRange类添加快速枚举：

Add fast enumeration to a DateRange class:

- (NSUInteger)countByEnumeratingWithState: (NSFastEnumerationState *)state
                                  objects: (id *)stackbuf
                                    count: (NSUInteger)len;
{
    NSInteger days = 0;
    id current = nil;
    id components = nil;
    if (state->state == 0)
    {
        current = [NSCalendar currentCalendar];
        state->mutationsPtr = &state->extra[0];
        components = [current components: NSDayCalendarUnit
                                fromDate: startDate
                                  toDate: endDate
                                 options: 0];
        days = [components day];
        state->extra[0] = days;
        state->extra[1] = (uintptr_t)current;
        state->extra[2] = (uintptr_t)components;
    } else {
        days = state->extra[0];
        current = (NSCalendar *)(state->extra[1]);
        components = (NSDateComponents *)(state->extra[2]);
    }
    NSUInteger count = 0;
    if (state->state <= days) {
        state->itemsPtr = stackbuf;
        while ( (state->state <= days) && (count < len) ) {
            [components setDay: state->state];
            stackbuf[count] = [current dateByAddingComponents: components
                                                       toDate: startDate
                                                      options: 0];
            state->state++;
            count++;
        }
    }
    return count;
}

这是丑陋的，但丑陋只限于我的日期范围类。我的客户端代码只是：

This is ugly, but the ugliness is confined to my date range class. My client code is just:

for (id date in dateRange) {
    NSLog( @"%@ in [%@,%@]", date, startDate, endDate );
}

我认为这可能是一个很好的原因创建一个DateRange类如果你没有一个。

I think this is probably a good enough reason to create a DateRange class if you don't have one already.

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