按日期（yyyy / MM / dd）与NSFetchRequest组合 [英] group by date (yyyy/MM/dd) with NSFetchRequest

问题描述

我必须计数和分组更多的3个属性。
我正在拉我的头发，而分组和计数字段与日期（yyyy / mm / dd HH：mm：ss）
我想按年 - 月 - 日分组，忽略时间。但我仍然需要时间的细节视图。时区在这里起着很大的作用。所以我只是保存它的utc格式。

i have to count and group on more that 3 properties. i'm pulling my hair while grouping and counting on field with date (yyyy/mm/dd HH:mm:ss) i want to group by year - month - day and ignore the time. but i still need the time for detail view. time zone plays a big role here. so i just save it in utc format.

NSFetchRequest *fetchRequest    = [[NSFetchRequest alloc] init];
NSEntityDescription *entity     = [NSEntityDescription entityForName:@"logs"
                                              inManagedObjectContext:context;
NSAttributeDescription* att3 = [entity.attributesByName objectForKey:@"savedDate"];
NSExpression *keyPathExpression3 = [NSExpression expressionForKeyPath: @"savedDate"];
NSExpression *countExpression3 = [NSExpression expressionForFunction: @"count:"
                                                           arguments: [NSArray arrayWithObject:keyPathExpression3]];
NSExpressionDescription *att3Description = [[NSExpressionDescription alloc] init];
[expressionDescription3 setName: @"countSavedDate"];
[expressionDescription3 setExpression: countExpression3];
[expressionDescription3 setExpressionResultType: NSInteger32AttributeType];

...

[fetchRequest setPropertiesToFetch:[NSArray arrayWithObjects:att1, att1Description, att2, att2Description, att3, att3Description, att4Description, att4, nil]];
[fetchRequest setPropertiesToGroupBy:[NSArray arrayWithObjects:att1, att2, att2, att3, nil]];
[fetchRequest setResultType:NSDictionaryResultType];

如何按日期分组（yyyy / MM / dd）？并且可以转换为UTC？

how can i can group by date (yyyy/MM/dd)? and be ok for converting to UTC?

提前感谢

ps：工作和无法获取。

ps: group by on a transient property doesnt work and cant be fetched.

推荐答案

我不得不转换日期的本地时区与fecth结果控制器如下

i had to convert date on the fly for local timezone with the fecth result controller as follow

[self willAccessValueForKey:@"startDateTime"];

NSDate * date = [self valueForKey:@"startDateTime"];

NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setCalendar:[NSCalendar currentCalendar]];
[formatter setTimeZone:[NSTimeZone localTimeZone]];
[formatter setDoesRelativeDateFormatting:YES];
[formatter setDateStyle:NSDateFormatterShortStyle];
[formatter setTimeStyle:NSDateFormatterNoStyle];
NSString *tmpValue = [formatter stringFromDate:date];
[self didAccessValueForKey:@"callStartDateTime"];

然后手动对它们进行分组，并且表视图现在使用数组而不是fetch result controller。

then manually group them and table view now use an array instead of fetch result controller.

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