用于一对多的 iOS Core 数据谓词

Question

如图所示，我有两个实体。我需要获取一个特定的约会和所有未删除与会者的相关与会者（hasDeleted ！= 1）。我尝试过不同的谓词格式。以下是我尝试过的两个主要谓词，但无法使这些谓词中的任何一个起作用。你能帮我解决这个问题吗？

NSPredicate *predicate1 = [NSPredicate predicateWithFormat:@"objectName = %@ AND objectId = %i AND SUBQUERY(attendees, $x, $x.hasDeleted != 1).@count != 0", [self.userDefaults stringForKey:OBJECT_NAME], [[self.userDefaults objectForKey:OBJECT_ID] intValue]];
NSPredicate *predicate2 = [NSPredicate predicateWithFormat:@"objectName = %@ AND objectId = %i AND (ANY attendees.hasDeleted != 1)", [self.userDefaults stringForKey:OBJECT_NAME], [[self.userDefaults objectForKey:OBJECT_ID] intValue]];

约会列表表格视图

可以查看与会者详细信息的详细约会视图。

获取结果控制器代码：

- (NSFetchedResultsController *)fetchedResultsController
{
    if (_fetchedResultsController != nil) {
        return _fetchedResultsController;
    }
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Attendee" inManagedObjectContext:self.managedObjectContext];
    [fetchRequest setEntity:entity];

    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"uuid" ascending:NO];
    NSArray *sortDescriptors = @[sortDescriptor];

    [fetchRequest setSortDescriptors:sortDescriptors];

    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"appointment.objectName = %@ AND appointment.objectId = %i AND hasDeleted != 1", [self.userDefaults stringForKey:OBJECT_NAME], [[self.userDefaults objectForKey:OBJECT_ID] intValue]];

    [fetchRequest setPredicate:predicate];

    NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:nil];
    aFetchedResultsController.delegate = self;
    self.fetchedResultsController = aFetchedResultsController;

    NSError *error = nil;
    if (![self.fetchedResultsController performFetch:&error]) {
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }
    return _fetchedResultsController;
}

Answer 1

获取请求总是从托管对象上下文返回对象。你不能 获取“修改后的对象”，例如具有修改关系的约会对象 “参加者”，仅包含具有特定属性的参加者。

您可以改为获取未删除的 Attendee 对象 这与给定的约会有关。 为参加者实体创建一个获取请求并使用谓词

[NSPredicate predicateWithFormat:@"appointment.objectName = %@ AND appointment.objectId = %i AND hasDeleted != 1", [self.userDefaults stringForKey:OBJECT_NAME], [[self.userDefaults objectForKey:OBJECT_ID] intValue]]

---

更新 根据新信息：在您的第一个视图控制器中，您使用 Appointment 实体的获取请求的获取结果控制器。 如果您只想显示有任何与会者尚未取消的约会 然后添加谓词

[NSPredicate predicateWithFormat:"ANY attendees.hasDeleted != 1"]

到这个获取请求。

当用户点击约会时，您将选择的约会传递到下一个视图 控制器。要显示此约会的与会者，请使用获取的结果 控制器对 Attendee 实体有一个获取请求，并添加谓词

[NSPredicate predicateWithFormat:@"appointment = %@ AND hasDeleted != 1", selectedAppointment]