NSFetchRequest 还获取我的实体类型的子类

Posted 2023-03-05

【中文标题】NSFetchRequest 还获取我的实体类型的子类

【英文标题】：NSFetchRequest fetches also subclasses of my entity type

【发布时间】：2013-11-21 10:12:07

【问题描述】：

我在表格视图中使用获取的结果控制器，一切正常，除了请求还获取我的实体类型的子类，而我不会。有没有办法做到这一点？控制器以通常的方式实例化。

- (NSFetchedResultsController *)fetchedResultsController

    if (_fetchedResultsController != nil) 
        return _fetchedResultsController;
    

    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    // Edit the entity name as appropriate.
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Event" inManagedObjectContext:self.managedObjectContext];
    [fetchRequest setEntity:entity];

    // Set the batch size to a suitable number.
    [fetchRequest setFetchBatchSize:20];

    // Edit the sort key as appropriate.
    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"date" ascending:NO];
    NSArray *sortDescriptors = @[sortDescriptor];

    [fetchRequest setSortDescriptors:sortDescriptors];

    // Edit the section name key path and cache name if appropriate.
    // nil for section name key path means "no sections".
    [NSFetchedResultsController deleteCacheWithName:@"Events"];
    NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:@"Events"];
    aFetchedResultsController.delegate = (id)self;
    self.fetchedResultsController = aFetchedResultsController;

    NSError *error = nil;
    if (![self.fetchedResultsController performFetch:&error]) 
        // Replace this implementation with code to handle the error appropriately.
        // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    

    return _fetchedResultsController;

【参考方案1】：

如果有人需要：

[fetchRequest setIncludesSubentities:NO];

如果你设置了这个属性，你只会得到设置的实体类型。