Question

我第一次使用Coredata，我正在为userinfo实体设置一些值，从usergroups实体中获取一些值。

在执行此过程时，我的应用程序崩溃了：

'项目之前没有为其主键分配对象ID field，用于获取Core Data的永久ID 宾语。在调用保存在managedObjectContext上之前，请务必分配对象ID。

这看起来像

[newManagedObject setValue:[newManagedObject assignObjectId] forKey:[newManagedObject
 primaryKeyField]]

。有问题的项目是：

 <Userinfo: 0x10695b30>  (entity: Userinfo; id: 0x10695b70  <x-coredata://18875EDC-D300-4D63-90FC-181B2487599D-3229-000024DF842CC304/Userinfo/tA6216695-816F-4379-B24C-984AAFD1A8342>; data:

//阅读价值观＆amp;修改

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Userinfo" inManagedObjectContext:context];
    [fetchRequest setEntity:entity];
    NSPredicate *datapredicate = [NSPredicate predicateWithFormat:@"username == %@",usermobileNumber];
    [fetchRequest setPredicate:datapredicate];

    [context executeFetchRequest:fetchRequest onSuccess:^(NSArray *results){
        NSLog(@"results %@",[results valueForKey:@"firstname"]);
        userinfoObject = [results objectAtIndex:0];
        NSLog(@"userinfo %@",userinfoObject);
//        userinfoObject = [[Userinfo alloc]initWithEntity:[NSEntityDescription entityForName:@"Userinfo" inManagedObjectContext:context] insertIntoManagedObjectContext:context];

        [userinfoObject setValue:[userinfoObject valueForKey:@"firstname"] forKey:@"firstname"];
        [userinfoObject setValue:[userinfoObject valueForKey:@"lastname"] forKey:@"lastname"];
        [userinfoObject setValue:[userinfoObject valueForKey:@"email"] forKey:@"email"];
        [userinfoObject setValue:[userinfoObject valueForKey:@"zipcode"] forKey:@"zipcode"];
        [userinfoObject setValue:[userinfoObject valueForKey:@"password"] forKey:@"password"];
        [userinfoObject setValue:[userinfoObject valueForKey:@"dateofbirth"] forKey:@"dateofbirth"];
        [userinfoObject setValue:[userinfoObject valueForKey:@"username"] forKey:@"username"];
        [userinfoObject setValue:[userinfoObject valueForKey:@"salutation"] forKey:@"salutation"];
//        [userinfoObject setValue:[userinfoObject assignObjectId] forKey:[userinfoObject primaryKeyField]];

//添加值

Usergroups *userGroupsObject = [NSEntityDescription insertNewObjectForEntityForName:@"Usergroups" inManagedObjectContext:context];
            [userGroupsObject setValue:contactObject.strGroupName forKey:@"groupname"];
            [userGroupsObject setValue:[contactsStack objectAtIndex:i] forKey:@"mobile_contacts"];
            [userGroupsObject setValue:usermobileNumber forKey:@"mobile_number"];
            [userGroupsObject setValue:[userGroupsObject assignObjectId] forKey:[userGroupsObject primaryKeyField]];
            NSError *error = nil;
            if (![context saveAndWait:&error]) {
                NSLog(@"There was an error! %@", error);
            }
            else {
                NSLog(@"You created Usergroup object!");
            }
            [userinfoObject addUsergroupsObject:userGroupsObject];

Answer 1

你应该提供更多代码..........

通常添加新条目将如下所示

FormField *info = [NSEntityDescription
                    insertNewObjectForEntityForName:@"FormField"
                    inManagedObjectContext:managedObjectContext];


[info setValue: @"string data to insert" forKey:@"fieldValue"];
NSError *error;
[managedObjectContext save:&error]

并检索条目将如下所示

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
[fetchRequest setEntity:[NSEntityDescription entityForName:@"entityName"
                                    inManagedObjectContext:managedObjectContext]];

NSError *error;
NSArray* data_ = [managedObjectContext executeFetchRequest:fetchRequest error:&error];

Answer 2

assignObjectID和primaryKeyField方法正在抛弃那些试图回答这个问题的人，因为他们是StackMob特定的方法。它们根本不直接与Core Data ID交互，它们只是将一个随机生成的UUID分配给一个属性，该属性映射到数据库中的主键字段（StackMob服务器）。事实上，在调用save之前必须这样做，因为增量存储实现然后使用该字符串ID在重写的obtainPermanentIDsForObjects：方法中创建永久的Core Data ID。

我的猜测是，您有一个托管对象，在保存之前，永远不会为该属性分配一个映射到数据库主键字段的值。在导致崩溃的保存之前，设置断点并打印出托管对象上下文的插入对象（即[self.managedObjectContext insertedObjects]）。这应该可以让您了解导致崩溃的对象，并且可以相应地调整代码。

应用程序在其主键字段的对象ID的核心数据中崩溃

2 个答案: