Question

我有NSDates的NSMutableArray，有些日期是在同一天。获取特定日期的NSDates数量的最佳方法是什么？

编辑：

对不起，我没有完全解释。我需要某种逻辑来从源数组中获取特定日期的日期数。所以我遍历数组，找到确切的日期，我需要知道同一天数组中有多少天。

Answer 1

修改

NSDate *sourceDate = theDateThatYouAreLookingFor; NSCalendar *calendar = [NSCalendar currentCalendar]; [calendar setTimeZone:[NSTimeZone systemTimeZone]]; NSDateComponents *dateComponents = [calendar components:(NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit) fromDate:sourceDate]; NSInteger day = [dateComponents day]; NSInteger month = [dateComponents month]; NSInteger year = [dateComponents year]; int count = 0; //add check for existing dates on the same day for(NSDate *checkDate in datesArray) { dateComponents = [calendar components:(NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit) fromDate:checkDate]; NSInteger checkDay = [dateComponents day]; NSInteger checkMonth = [dateComponents month]; NSInteger checkYear = [dateComponents year]; if(checkDay == day && checkMonth == month && checkYear == year) count++; } //do something with count

结束编辑

最简单的方法是遍历数组并使用NSDateFormatter将每个日期的日期作为字符串进行比较。请记住，NSDateFormatters很昂贵，所以你不想经常执行这个过程。

您可以这样做：

NSMutableDictionary *dateInfo = [NSMutableDictionary dictionary]; NSDateFormatter *formatter = [[NSDateFormatter alloc]init]; formatter.locale = [NSLocale currentLocale]; formatter.dateFormat = @"yyyyMMdd"; for(NSDate *date in datesArray) { NSString *dateStr = [formatter stringFromDate:date]; NSNumber *currentCount = [dateInfo objectForKey:dateStr]; if(currentCount) { //bump value [dateInfo setObject:[NSNumber numberWithInt:currentCount.intValue + 1] forKey:dateStr]; } else { [dateInfo setObject:[NSNumber numberWithInt:1] forKey:dateStr]; } }

Answer 2

出于性能原因，我会创建两个日期，“今天”（00:00:00）和“明天”（00:00:00）。您可以将这些日期用作比较的边界。如果日期等于或大于今天且小于明天则是匹配。

由于NSDate比较基本上是双（原始类型）比较，因此此方法比比较NSString对象或NSDateComponents更快。要创建NSDateComponents，需要使用大量数学，NSDateFormatters本身可能使用NSDateComponents。

NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];

NSDateComponents *todayComponents = [[NSDateComponents alloc] init];
todayComponents.year = 2013;
todayComponents.month = 6;
todayComponents.day = 21;

// today must be at the beginning of your search day. i.e. 00:00:00
NSDate *today = [calendar dateFromComponents:todayComponents]; 

NSDateComponents *oneDayOffset = [[NSDateComponents alloc] init];
oneDayOffset.day = 1;
NSDate *tomorrow = [calendar dateByAddingComponents:oneDayOffset toDate:today options:0];

NSIndexSet *todaysIndexes = [array indexesOfObjectsPassingTest:^BOOL(id obj, NSUInteger idx, BOOL *stop) {
    if ([(NSDate *)obj compare:today] != NSOrderedAscending && [(NSDate *)obj compare:tomorrow] == NSOrderedAscending) {
//       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ obj is not earlier than "today" (= same time or later)
//                                                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ obj is earlier than "tomorrow"            
        return YES;
    }
    return NO;
}];

NSLog(@"%d", [todaysIndexes count]);

今天替换您的搜索日期（午夜），您就可以开始了。

带有NSDate条目的NSMutableArray获取天数

2 个答案: