使用fetchedresultcontroller为每个月设置不同的部分

问题描述

我试图将我的tableview分成每个月的部分。我开始使用苹果的示例。首先，我在我的核心数据库中添加了一个属性sectionIdentifier。然后在我的managedobject子类中，我添加了这个方法。

   - （NSString *）sectionIdentifier {
 
 / /根据需要创建和缓存段标识符。 
 
 [self willAccessValueForKey：@sectionIdentifier]; 
 NSString * tmp = [self primitiveSectionIdentifier]; 
 [self didAccessValueForKey：@sectionIdentifier]; 
 
 if（！tmp）{
 / * 
节按月和年组织。创建段标识符作为表示数字的字符串（年* 1000）+月;这样，他们将按照时间顺序正确地排序，而不管月份的实际名称。 
 * / 
 NSCalendar * calendar = [NSCalendar currentCalendar]; 
 
 NSDateComponents * components = [日历组件：（NSYearCalendarUnit | NSMonthCalendarUnit）fromDate：[self date]]; 
 tmp = [NSString stringWithFormat：@％d，（[components year] * 1000）+ [components month]]; 
 [self setPrimitiveSectionIdentifier：tmp]; 
} 
 NSLog（@tmp：％@，tmp）; 
 return tmp; 
} 
  

这是我在我的titleForHeaderSection

- （NSString *）tableView：（UITableView *）tableView titleForHeaderInSection：（NSInteger）section {
id< NSFetchedResultsSectionInfo> theSection = [[self.fetchedResultsController sections] objectAtIndex：section];


/ *
节信息来自事件的sectionIdentifier，它是一个表示数字（年* 1000）+月的字符串。
要显示节标题，请将年份和月份组件转换为字符串表示形式。
* /
static NSArray * monthSymbols = nil;

if（！monthSymbols）{
NSDateFormatter * formatter = [[NSDateFormatter alloc] init];
[formatter setCalendar：[NSCalendar currentCalendar]];
monthSymbols = [formatter monthSymbols];
}

NSInteger numericSection = [[TheSection name] integerValue];

NSInteger year = numericSection / 1000;
NSInteger month = numericSection - （year * 1000）;

NSString * titleString = [NSString stringWithFormat：@％@％d，[monthSymbols objectAtIndex：month-1]，year];
NSLog（@titelstring is：％@，titleString）;
return titleString;
}


对于我的行数InSection我这样做。

  id< NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex：section]; 
 
 NSInteger count = [sectionInfo numberOfObjects]; 
 return count; 
  

这是我的NumberOfSectionsInTableview

  NSInteger count = [[self.fetchedResultsController sections] count]; 
 return count; 
  

有人可以帮忙吗？

提前！

发生了什么问题

打印我的日志NSLog（@tmp：％@，tmp）;
并且我得到以下错误：

  CoreData：error：（NSFetchedResultsController）名称键路径'sectionIdentifier'。对象将被放置在未命名的部分
 2012-10-10 10：41：17.475 RacingGenk [15785：c07] ***由于未捕获异常NSRangeException终止应用程序，原因：' -  [__ NSCFArray objectAtIndex：]：索引（-1（或可能更大））超出范围（12）'
  

解决方案

一个常见的错误通常编码nsmanagedobject的瞬态属性，是人们忘记了在数据模型文件（xcdatamodeld）中启用瞬态属性。

I am trying to split my tableview into sections for each month. I start working with the DateSectionTitles example of apple. First of all I added in my core database a attribute 'sectionIdentifier'. Then in my managedobject subclass I added this method.

- (NSString *)sectionIdentifier {

    // Create and cache the section identifier on demand.

    [self willAccessValueForKey:@"sectionIdentifier"];
    NSString *tmp = [self primitiveSectionIdentifier];
    [self didAccessValueForKey:@"sectionIdentifier"];

    if (!tmp) {
        /*
         Sections are organized by month and year. Create the section identifier as a string representing the number (year * 1000) + month; this way they will be correctly ordered chronologically regardless of the actual name of the month.
         */
        NSCalendar *calendar = [NSCalendar currentCalendar];

        NSDateComponents *components = [calendar components:(NSYearCalendarUnit | NSMonthCalendarUnit) fromDate:[self date]];
        tmp = [NSString stringWithFormat:@"%d", ([components year] * 1000) + [components month]];
          [self setPrimitiveSectionIdentifier:tmp];
    }
    NSLog(@"tmp: %@",tmp);
    return tmp;
}

This is what i do in my titleForHeaderSection

- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {
        id <NSFetchedResultsSectionInfo> theSection = [[self.fetchedResultsController sections] objectAtIndex:section];


    /*
     Section information derives from an event's sectionIdentifier, which is a string representing the number (year * 1000) + month.
     To display the section title, convert the year and month components to a string representation.
     */
    static NSArray *monthSymbols = nil;

    if (!monthSymbols) {
        NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
        [formatter setCalendar:[NSCalendar currentCalendar]];
        monthSymbols = [formatter monthSymbols];
    }

    NSInteger numericSection = [[theSection name] integerValue];

    NSInteger year = numericSection / 1000;
    NSInteger month = numericSection - (year * 1000);

    NSString *titleString = [NSString stringWithFormat:@"%@ %d", [monthSymbols objectAtIndex:month-1], year];
    NSLog(@"titelstring is: %@",titleString);
    return titleString;
}

For my number of rowsInSection I do this.

id <NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex:section];

        NSInteger count = [sectionInfo numberOfObjects];
        return count;

And this for my NumberOfSectionsInTableview

NSInteger count = [[self.fetchedResultsController sections] count];
        return count;

Can anybody help?

Thanks in advance!

What is going wrong

First off all it don't prints my log in NSLog(@"tmp: %@",tmp);And also I get the following error:

CoreData: error: (NSFetchedResultsController) A section returned nil value for section name key path 'sectionIdentifier'. Objects will be placed in unnamed section
2012-10-10 10:41:17.475 RacingGenk[15785:c07] *** Terminating app due to uncaught exception 'NSRangeException', reason: '-[__NSCFArray objectAtIndex:]: index (-1 (or possibly larger)) beyond bounds (12)'

解决方案

One common mistake usually coding transient property for nsmanagedobject, is people forget to also "enable" transient property in the data model file (xcdatamodeld).

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