日期为 sectionNameKeyPath 的 NSFetchedResultsController [英] A NSFetchedResultsController with date as sectionNameKeyPath

问题描述

我开发了一个使用 Core Data 的应用程序.在一个 UITableView 中，我想显示我的实体列表，按对象的保存日期排序.当我这样做时:

I develop an application which uses Core Data. In one UITableView, I want to display a list of my entities, sorted by the saved date of the objects. When I do this:

fetchedResultsController = [[NSFetchedResultsController alloc]
                            initWithFetchRequest:fetchRequest
                            managedObjectContext:managedObjectContext
                              sectionNameKeyPath:@"date"
                                       cacheName:nil];

我为每个对象获得了一个新部分，因为此代码也根据秒对日期进行分组.但我想要一个按日期分组的对象列表，但只能按日、月和年分组.是否可能以及如何实现?

I get for each object a new section because this code groups the dates according to the seconds, too. But I want a list of the objects, grouped by date, but only according to the day, month and year. Is it possible and how?

非常感谢您的帮助！！;)

Thank you very much for your help!! ;)

推荐答案

这应该对你有用:

- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {
  NSString *rawDateStr = [[[self.fetchedResultsController sections] objectAtIndex:section] name];
  // Convert rawDateStr string to NSDate...
  NSDateFormatter *formatter = [[[NSDateFormatter alloc] init] autorelease];
  [formatter setDateFormat:@"yyyy-MM-dd HH:mm:ss ZZ"];
  NSDate *date = [formatter dateFromString:rawDateStr];

  // Convert NSDate to format we want...
  [formatter setDateFormat:@"d MMMM yyyy"];
  NSString *formattedDateStr = [formatter stringFromDate:date];
  return formattedDateStr;  
}

Jus 看到了您的评论以及您想要实现的目标，您可以创建一个瞬态 NSDate 属性(非持久性)，其格式与上述代码类似(即没有 H:mm:ss ZZZZ) 并将该属性用作您的 sectionNameKeyPath 值.

Jus saw your comment and for what you are trying to achieve, you could create a transient NSDate attribute (non persistent) that is formatted in a similar way to the above code (i.e. without H:mm:ss ZZZZ) and use that attribute as your sectionNameKeyPath value.

简而言之，对于 foo 对象，具有 fooDate 和 fooDateTransient 属性，您将:

So in a nutshell for a foo object, with fooDate and fooDateTransient attributes, you would:

1. 获取您的 foo.fooDate 属性

使用上面的代码(或类似代码)对其进行转换，并将 NSDate 结果分配给 foo.fooDateTransient

Transform it using the code above (or similar) and assign the NSDate result to foo.fooDateTransient

在创建 fetchedResultsController 对象时，使用 fooDateTransient 作为您的 sectionNameKeyPath.

Use fooDateTransient as your sectionNameKeyPath when creating the fetchedResultsController object.

PS:我自己还没有测试过，但应该值得一试！

PS: I haven't tested this myself but should be worth a shot!

祝你好运罗格

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