具有关系属性性能问题的核心数据sectionNameKeyPath

Question

具有关系属性性能问题的核心数据sectionNameKeyPath

Raz*_*van 5 core-data objective-c uitableview nsfetchedresultscontroller ios

我有一个核心数据模型,包括三个实体:
Person,Group,Photo它们之间的关系如下:

人<< ----------->组(一对多关系)
人<------------->照片(一对一)

当我使用NSFetchedResultsControllerin a 执行提取时UITableView,我想Person使用Group's entity name属性对对象进行分组.

为此,我用sectionNameKeyPath:@"group.name".

问题在于,当我使用Group关系中的属性时,在我滚动的时候,NSFetchedResultsController在小批量的20(我有setFetchBatchSize: 20)中提前取出所有内容而不是获取批次tableView.

如果我使用Person实体的属性(比如sectionNameKeyPath:@"name")来创建部分,一切正常:在NSFetchResultsController滚动时加载小批量的20个对象.

我用来实例化NSFetchedResultsController的代码:

- (NSFetchedResultsController *)fetchedResultsController {

    if (_fetchedResultsController) {
        return _fetchedResultsController;
    }

    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:[Person description]
                                              inManagedObjectContext:self.managedObjectContext];

    [fetchRequest setEntity:entity];

    // Specify how the fetched objects should be sorted
    NSSortDescriptor *groupSortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"group.name"
                                                                        ascending:YES];

    NSSortDescriptor *personSortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"birthName"
                                                                         ascending:YES
                                                                          selector:@selector(localizedStandardCompare:)];


    [fetchRequest setSortDescriptors:[NSArray arrayWithObjects:groupSortDescriptor, personSortDescriptor, nil]];

    [fetchRequest setRelationshipKeyPathsForPrefetching:@[@"group", @"photo"]];
    [fetchRequest setFetchBatchSize:20];

    NSError *error = nil;
    NSArray *fetchedObjects = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error];

    if (fetchedObjects == nil) {
        NSLog(@"Error Fetching: %@", error);
    }

    _fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest
                                                                    managedObjectContext:self.managedObjectContext sectionNameKeyPath:@"group.name" cacheName:@"masterCache"];

    _fetchedResultsController.delegate = self;

    return _fetchedResultsController;
}

Run Code Online (Sandbox Code Playgroud)

如果我在"group.name"没有与App的UI交互的情况下创建部分,这就是我在Instruments中得到的: 按关系获取核心数据