CoreData：在保存操作后，相同的谓词（IN）返回不同的提取结果 [英] CoreData: Same predicate (IN) returns different fetched results after a Save operation
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问题描述
巨大更新：
我创建了一个全新的项目来模仿这个问题，它一直出现！
这是我的数据模型：
任务具有指向 Person的一对多关系。
@interface Person：NSManagedObject
@property（nonatomic，retain）NSString * personId;
@property（nonatomic，retain）NSString * name;
@end
//
@class Person;
@interface任务：NSManagedObject
@property（nonatomic，retain）NSNumber * taskId;
@property（nonatomic，retain）NSSet * watchers;
@end
@interface任务（CoreDataGeneratedAccessors）
- （void）addWatchersObject：（Person *）value;
- （void）removeWatchersObject：（Person *）value;
- （void）addWatchers：（NSSet *）values;
- （void）removeWatchers：（NSSet *）values;
@end
现在，我创建两个人，p1& p2和两个任务，1001& 1002：
- （void）viewDidLoad
{
[super viewDidLoad];
//在加载视图之后执行任何其他设置，通常来自nib。
人* p1 = [self insertOrUpdatePerson：@111withName：@aaa];
Person * p2 = [self insertOrUpdatePerson：@222withName：@bbb];
[self insertOrUpdateTask：1001 withWatcher：p1];
[self insertOrUpdateTask：1001 withWatcher：p2];
[self insertOrUpdateTask：1002 withWatcher：p1];
[self insertOrUpdateTask：1002 withWatcher：p2];
NSArray * watchedTasks = nil;
watchedTasks = [self fetchTasksWatchedByPerson：p1]; // return 2 objects
NSLog（@watchedTasks：％@ \\\
，watchedTasks）;
[self saveContext];
watchedTasks = [self fetchTasksWatchedByPerson：p1]; // return 1 objects
NSLog（@watchedTasks：％@ \\\
，watchedTasks）;
NSArray * allTasks = [self fetchAllTasks]; // return 2 objects
NSLog（@allTasks：％@ \\\
，watchedTasks）;
}
并且日志如下。 请注意，watchedTasks的第二个输出只有一个对象！
打印watchedTasks的描述：
< __ NSArrayI 0x8d5aff0>（
< Task：0x8d5b240>（entity：Task; id：0x8d5b3e0< x-coredata：// 706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4 / Task / p2& ：{
taskId = 1002;
watchers =（
0x8d57f80< x-coredata：// 706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4 / Person / p2>，
0x8d56070< x-coredata：// 706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4 / Person / p1"
）;
}），
< Task：0x8d59d10& entity：task; id：0x8d59420< x-coredata：// 706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4 / Task / p1> ;; data：{
taskId = 1001;
watchers = $ b0x8d57f80< x-coredata：// 706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4 / Person / p2>，
0x8d56070< x-coredata：// 706EB8CA-ACE7-48DB-89E1- 7CCFCDD41DA4 / Person / p1>
）;
}）
）
打印updateObjects的描述：
< __ NSArrayI 0x8e41880>（
< Task：0x8d59d10> （entity：Task; id：0x8d59420< x-coredata：// 706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4 / Task / p1> ;; data：{
taskId = 1001;
watchers = b $ b0x8d57f80< x-coredata：// 706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4 / Person / p2>，
0x8d56070< x-coredata：// 706EB8CA-ACE7-48DB-89E1 -7CCFCDD41DA4 / Person / p1>
）;
}），
< Task：0x8d5b240> （entity：Task; id：0x8d5b3e0< x-coredata：// 706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4 / Task / p2> ;; data：{
taskId = 1002;
watchers = b $ b0x8d57f80< x-coredata：// 706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4 / Person / p2>，
0x8d56070< x-coredata：// 706EB8CA-ACE7-48DB-89E1 -7CCFCDD41DA4 / Person / p1>
）;
}），
< Person：0x8d56cc0> （entity：Person; id：0x8d56070< x-coredata：// 706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4/ Person / p1> ;; data：{
name = aaa;
personId = 111;
}），
< Person：0x8d57be0> （entity：Person; id：0x8d57f80< x-coredata：// 706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4/ Person / p2> ;; data：{
name = bbb;
personId = 222;
}）
）
打印watchedTasks的描述：
< _PFArray 0x8f57da0>（
< Task：0x8d5b240>（entity：Task; id ：0x8d5b3e0< x-coredata：// 706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4 / Task / p2> ;; data：{
taskId = 1002;
watchers =（
0x8d57f80< ; x-coredata：// 706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4 / Person / p2>，
0x8d56070< x-coredata：// 706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4 / Person / p1> ;
）;
}）
）
打印allTasks的描述：
< _PFArray 0x8e44b30>（
< 0x8d59d10>（entity：Task; id：0x8d59420< x-coredata：// 706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4 / Task / p1> ;; data：{
taskId = 1001;
watchers = （
0x8d57f80< x-coredata：// 706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4 / Person / p2>，
0x8d56070< x-coredata：// 706EB8CA-ACE7-48DB -89E1-7CCFCDD41DA4 / Person / p1>
）;
}），
< Task：0x8d5b240> （entity：Task; id：0x8d5b3e0< x-coredata：// 706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4 / Task / p2> ;; data：{
taskId = 1002;
watchers = b $ b0x8d57f80< x-coredata：// 706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4 / Person / p2>，
0x8d56070< x-coredata：// 706EB8CA-ACE7-48DB-89E1 -7CCFCDD41DA4 / Person / p1>
）;
}）
）
（lldb）
所以我打开.sqlite文件看看到底是什么。
我惊讶的是，
watchers在Person表中，不是在中间/映射Task2Person表中。我记得一旦关系存在于中间表中。
然后，
watchers人表只包含一个值，而不是集合或数组！- （void）viewDidLoad
{
[super viewDidLoad];
//在加载视图之后执行任何其他设置，通常来自nib。
NSArray * watchedTasks = nil;
人* p1 = [self insertOrUpdatePerson：@111withName：@aaa];
Person * p2 = [self insertOrUpdatePerson：@222withName：@bbb];
watchedTasks = [self fetchTasksWatchedByPerson：p1]; // return 1 object
任务* t1 = [self insertOrUpdateTask：1001 withWatcher：p1]; // update watchers in the memory
[self insertOrUpdateTask：1001 withWatcher：p2];
任务* t2 = [self insertOrUpdateTask：1002 withWatcher：p1];
[self insertOrUpdateTask：1002 withWatcher：p2];
watchedTasks = [self fetchTasksWatchedByPerson：p1]; // return 2 objects
[self saveContext];
watchedTasks = [self fetchTasksWatchedByPerson：p1]; // return 1 object
因此我发现在启动应用程序并从数据库中读取任务后文件，只返回1个对象。
当我更新任务的
watchers信息时，可以抓取两个对象。
最后在保存上下文之后，只有一个对象。
- 以下的旧信息
我有以下代码：
NSArray * existedTasks = [[TaskBizDB sharedInstance] fetchTasksWatchedByMeOfProject：projectId];
[context save：& error];
existedTasks = [[TaskBizDB sharedInstance] fetchTasksWatchedByMeOfProject：projectId];
NSArray * allTasks = [[TaskBizDB sharedInstance] fetchTasksOfProject：projectId];
- 第一行返回两个对象;
- 第二行保存上下文;
- 第三行返回只有一个对象
- 最后一行返回6个对象，包含在第一行返回的两个对象
。
fetch接口的工作原理如下：
WXModel * model = [WXModel modelWithEntity：NSStringFromClass（[WQPKTeamTask class]）];
NSPredicate * predicate = [NSPredicate predicateWithFormat：@（％@ IN personWatchers）AND（projectId ==％d），currentLoginUser，projectId];
[model setPredicate：predicate];
NSArray * fetchedTasks = [model fetch];
if（fetchedTasks.count == 0）return nil;
return fetchedTasks;让我困惑的是，使用相同的获取请求，为什么在保存后返回不同的结果？
这里有更多细节：
在第一行返回的两个对象是：
< WQPKTeamTask：0x1b92fcc0> （实体：WQPKTeamTask; id：0x1b9300f0 ; data：{
projectId = 372004;
taskId = 338001;
personWatchers =（
0xf0bf440< x-coredata：// CFFD3F8B-E613-4DE8-85AA-4D6DD08E88C5 / WWPerson / p1>
）;
}
< WQPKTeamTask：0xf3f6130>（实体：WQPKTeamTask; id：0xf3cb8d0 ; data：{
projectId = 372004;
taskId = 340006;
personWatchers =（
0xf0bf440< x-coredata：// CFFD3F8B-E613-4DE8-85AA-4D6DD08E88C5 / WWPerson / p1>
）;
}
在第三行返回的唯一一个对象是： p>
< WQPKTeamTask：0x1b92fcc0>（实体：WQPKTeamTask; id：0x1b9300f0< x-coredata：// CFFD3F8B-E613-4DE8- 85AA-4D6DD08E88C5 / WQPKTeamTask / p9> ;; data：{
projectId = 372004;
taskId = 338001;
personWatchers =（
0xf0bf440< x-coredata：// CFFD3F8B-E613-4DE8-85AA-4D6DD08E88C5 / WWPerson / p1>
）;
}
打印allTasks的说明：
< _PFArray 0xf30b9a0>（
< WQPKTeamTask：0xf3ab9d0>（entity：WQPKTeamTask; id：0xf3cda40< x-coredata：// CFFD3F8B-E613-4DE8 -85AA-4D6DD08E88C5 / WQPKTeamTask / p6>; data：< fault>），
< WQPKTeamTask：0xf315720>（entity：WQPKTeamTask; id：0xf3c23a0
taskId = 338001;
personWatchers =（
0xf0bf440< x-coredata：// CFFD3F8B-E613 -4DE8-85AA-4D6DD08E88C5 / WWPerson / p1>
）;
}），
< WQPKTeamTask：0xf325e50& （实体：WQPKTeamTask; id：0xf343820< x-coredata：// CFFD3F8B-E613-4DE8-85AA-4D6DD08E88C5 / WQPKTeamTask / p10>; data：< fault>），
< WQPKTeamTask：0xf3f6130& （实体：WQPKTeamTask; id：0xf3cb8d0 ; data：{
projectId = 372004;
taskId = 340006;
personWatchers =（
0xf0bf440< x-coredata：// CFFD3F8B-E613-4DE8-85AA-4D6DD08E88C5 / WWPerson / p1>
）;
}）
）
UPDATE 1
如果我调用 fetchTasksWatchedByMeOfProject：中的同一个界面：
#pragma mark - NSFetchedResultsController委托
- （void）controllerDidChangeContent：（NSFetchedResultsController *）controller
{
UPDATE 2
$ b b
我试过：
NSPredicate * predicate = [NSPredicate predicateWithFormat：@（ANY personWatchers ==％@）AND（projectId ==％d），currentLoginUser，projectId];
NSPredicate * predicate = [NSPredicate predicateWithFormat：@（ANY personWatchers.personId ==％@）AND（projectId ==％d），currentLoginUserId，projectId];
仍然有同样的结果。
3
我已检查过 save：&错误，错误是nil。
解决方案今天我和我的队友一起想出了这个问题。
例如任务有一对多关系 watchers 到 Person ，但 Person 没有与 Task 关系字段 watchers 将放在 Person 表中，而不是中间/映射表。
在此条件下，我将 Person p1添加到 Task t1's watchers 会将观察者更新为 1 然后，将 Person p1添加到 Person 表。
任务 t2， watchers 字段将更新为 2 如下：
/ p>
因此， Person 只能指向一个 Task ！
通过从 Person 添加一个反向关系到任务可以绕过这个问题。
HUGE UPDATE：
I create a totally new project to mimic the problem, it does appear all the time!
Here is my data model:
Task has a to-many relationship pointing to Person.
@interface Person : NSManagedObject
@property (nonatomic, retain) NSString * personId;
@property (nonatomic, retain) NSString * name;
@end
//
@class Person;
@interface Task : NSManagedObject
@property (nonatomic, retain) NSNumber * taskId;
@property (nonatomic, retain) NSSet *watchers;
@end
@interface Task (CoreDataGeneratedAccessors)
- (void)addWatchersObject:(Person *)value;
- (void)removeWatchersObject:(Person *)value;
- (void)addWatchers:(NSSet *)values;
- (void)removeWatchers:(NSSet *)values;
@end
Now, I create two persons, p1 & p2, and two tasks, 1001 & 1002:
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
Person *p1 = [self insertOrUpdatePerson:@"111" withName:@"aaa"];
Person *p2 = [self insertOrUpdatePerson:@"222" withName:@"bbb"];
[self insertOrUpdateTask:1001 withWatcher:p1];
[self insertOrUpdateTask:1001 withWatcher:p2];
[self insertOrUpdateTask:1002 withWatcher:p1];
[self insertOrUpdateTask:1002 withWatcher:p2];
NSArray *watchedTasks = nil;
watchedTasks = [self fetchTasksWatchedByPerson:p1]; // return 2 objects
NSLog(@"watchedTasks : %@\n", watchedTasks);
[self saveContext];
watchedTasks = [self fetchTasksWatchedByPerson:p1]; // return 1 objects
NSLog(@"watchedTasks : %@\n", watchedTasks);
NSArray *allTasks = [self fetchAllTasks]; // return 2 objects
NSLog(@"allTasks : %@\n", watchedTasks);
}
And the log follows. Notice that the second output of watchedTasks has only one object!
Printing description of watchedTasks:
<__NSArrayI 0x8d5aff0>(
<Task: 0x8d5b240> (entity: Task; id: 0x8d5b3e0 <x-coredata://706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4/Task/p2> ; data: {
taskId = 1002;
watchers = (
"0x8d57f80 <x-coredata://706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4/Person/p2>",
"0x8d56070 <x-coredata://706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4/Person/p1>"
);
}),
<Task: 0x8d59d10> (entity: Task; id: 0x8d59420 <x-coredata://706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4/Task/p1> ; data: {
taskId = 1001;
watchers = (
"0x8d57f80 <x-coredata://706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4/Person/p2>",
"0x8d56070 <x-coredata://706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4/Person/p1>"
);
})
)
Printing description of updateObjects:
<__NSArrayI 0x8e41880>(
<Task: 0x8d59d10> (entity: Task; id: 0x8d59420 <x-coredata://706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4/Task/p1> ; data: {
taskId = 1001;
watchers = (
"0x8d57f80 <x-coredata://706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4/Person/p2>",
"0x8d56070 <x-coredata://706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4/Person/p1>"
);
}),
<Task: 0x8d5b240> (entity: Task; id: 0x8d5b3e0 <x-coredata://706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4/Task/p2> ; data: {
taskId = 1002;
watchers = (
"0x8d57f80 <x-coredata://706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4/Person/p2>",
"0x8d56070 <x-coredata://706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4/Person/p1>"
);
}),
<Person: 0x8d56cc0> (entity: Person; id: 0x8d56070 <x-coredata://706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4/Person/p1> ; data: {
name = aaa;
personId = 111;
}),
<Person: 0x8d57be0> (entity: Person; id: 0x8d57f80 <x-coredata://706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4/Person/p2> ; data: {
name = bbb;
personId = 222;
})
)
Printing description of watchedTasks:
<_PFArray 0x8f57da0>(
<Task: 0x8d5b240> (entity: Task; id: 0x8d5b3e0 <x-coredata://706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4/Task/p2> ; data: {
taskId = 1002;
watchers = (
"0x8d57f80 <x-coredata://706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4/Person/p2>",
"0x8d56070 <x-coredata://706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4/Person/p1>"
);
})
)
Printing description of allTasks:
<_PFArray 0x8e44b30>(
<Task: 0x8d59d10> (entity: Task; id: 0x8d59420 <x-coredata://706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4/Task/p1> ; data: {
taskId = 1001;
watchers = (
"0x8d57f80 <x-coredata://706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4/Person/p2>",
"0x8d56070 <x-coredata://706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4/Person/p1>"
);
}),
<Task: 0x8d5b240> (entity: Task; id: 0x8d5b3e0 <x-coredata://706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4/Task/p2> ; data: {
taskId = 1002;
watchers = (
"0x8d57f80 <x-coredata://706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4/Person/p2>",
"0x8d56070 <x-coredata://706EB8CA-ACE7-48DB-89E1-7CCFCDD41DA4/Person/p1>"
);
})
)
(lldb)
So I open the .sqlite file to see what exactly in.
What surprise me first is that watchers is in the Person table, not in a middle/mapping Task2Person table. I remember that once the relationship exists in a middle table.
Then, the watchers field in the Person table contains only one value, not a set or array!
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
NSArray *watchedTasks = nil;
Person *p1 = [self insertOrUpdatePerson:@"111" withName:@"aaa"];
Person *p2 = [self insertOrUpdatePerson:@"222" withName:@"bbb"];
watchedTasks = [self fetchTasksWatchedByPerson:p1]; // return 1 object
Task *t1 = [self insertOrUpdateTask:1001 withWatcher:p1]; // update watchers in the memory
[self insertOrUpdateTask:1001 withWatcher:p2];
Task *t2 = [self insertOrUpdateTask:1002 withWatcher:p1];
[self insertOrUpdateTask:1002 withWatcher:p2];
watchedTasks = [self fetchTasksWatchedByPerson:p1]; // return 2 objects
[self saveContext];
watchedTasks = [self fetchTasksWatchedByPerson:p1]; // return 1 object
So I found that after I launch the App and read the tasks from the db file, only 1 object is returned.
When I update the watchers information for the tasks, 2 objects can be fetched.
Finally after I save the context, only 1 object again.
Just Ignore This
- Old Information Below
I have code below:
NSArray *existedTasks = [[TaskBizDB sharedInstance] fetchTasksWatchedByMeOfProject:projectId];
[context save:&error];
existedTasks = [[TaskBizDB sharedInstance] fetchTasksWatchedByMeOfProject:projectId];
NSArray *allTasks = [[TaskBizDB sharedInstance] fetchTasksOfProject:projectId];
- First line returns two objects;
- Second line save the context;
- Third line returns just one object, which is contained in the 'two objects' above;
- And the last line returns 6 objects, containing the 'two objects'
returned at the first line.
The fetch interface works like below:
WXModel *model = [WXModel modelWithEntity:NSStringFromClass([WQPKTeamTask class])];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(%@ IN personWatchers) AND (projectId == %d)", currentLoginUser, projectId];
[model setPredicate:predicate];
NSArray *fetchedTasks = [model fetch];
if (fetchedTasks.count == 0) return nil;
return fetchedTasks;
What confused me is that, with the same fetch request, why return different results just after a save?
Here comes more detail:
The 'two objects' returned at the first line are:
<WQPKTeamTask: 0x1b92fcc0> (entity: WQPKTeamTask; id: 0x1b9300f0 <x-coredata://CFFD3F8B-E613-4DE8-85AA-4D6DD08E88C5/WQPKTeamTask/p9> ; data: {
projectId = 372004;
taskId = 338001;
personWatchers = (
"0xf0bf440 <x-coredata://CFFD3F8B-E613-4DE8-85AA-4D6DD08E88C5/WWPerson/p1>"
);
}
<WQPKTeamTask: 0xf3f6130> (entity: WQPKTeamTask; id: 0xf3cb8d0 <x-coredata://CFFD3F8B-E613-4DE8-85AA-4D6DD08E88C5/WQPKTeamTask/p11> ; data: {
projectId = 372004;
taskId = 340006;
personWatchers = (
"0xf0bf440 <x-coredata://CFFD3F8B-E613-4DE8-85AA-4D6DD08E88C5/WWPerson/p1>"
);
}
And the only one object returned at third line is:
<WQPKTeamTask: 0x1b92fcc0> (entity: WQPKTeamTask; id: 0x1b9300f0 <x-coredata://CFFD3F8B-E613-4DE8-85AA-4D6DD08E88C5/WQPKTeamTask/p9> ; data: {
projectId = 372004;
taskId = 338001;
personWatchers = (
"0xf0bf440 <x-coredata://CFFD3F8B-E613-4DE8-85AA-4D6DD08E88C5/WWPerson/p1>"
);
}
Printing description of allTasks:
<_PFArray 0xf30b9a0>(
<WQPKTeamTask: 0xf3ab9d0> (entity: WQPKTeamTask; id: 0xf3cda40 <x-coredata://CFFD3F8B-E613-4DE8-85AA-4D6DD08E88C5/WQPKTeamTask/p6> ; data: <fault>),
<WQPKTeamTask: 0xf315720> (entity: WQPKTeamTask; id: 0xf3c23a0 <x-coredata://CFFD3F8B-E613-4DE8-85AA-4D6DD08E88C5/WQPKTeamTask/p7> ; data: <fault>),
<WQPKTeamTask: 0xf3a1ed0> (entity: WQPKTeamTask; id: 0xf3cda30 <x-coredata://CFFD3F8B-E613-4DE8-85AA-4D6DD08E88C5/WQPKTeamTask/p8> ; data: <fault>),
<WQPKTeamTask: 0x1b92fcc0> (entity: WQPKTeamTask; id: 0x1b9300f0 <x-coredata://CFFD3F8B-E613-4DE8-85AA-4D6DD08E88C5/WQPKTeamTask/p9> ; data: {
projectId = 372004;
taskId = 338001;
personWatchers = (
"0xf0bf440 <x-coredata://CFFD3F8B-E613-4DE8-85AA-4D6DD08E88C5/WWPerson/p1>"
);
}),
<WQPKTeamTask: 0xf325e50> (entity: WQPKTeamTask; id: 0xf343820 <x-coredata://CFFD3F8B-E613-4DE8-85AA-4D6DD08E88C5/WQPKTeamTask/p10> ; data: <fault>),
<WQPKTeamTask: 0xf3f6130> (entity: WQPKTeamTask; id: 0xf3cb8d0 <x-coredata://CFFD3F8B-E613-4DE8-85AA-4D6DD08E88C5/WQPKTeamTask/p11> ; data: {
projectId = 372004;
taskId = 340006;
personWatchers = (
"0xf0bf440 <x-coredata://CFFD3F8B-E613-4DE8-85AA-4D6DD08E88C5/WWPerson/p1>"
);
})
)
UPDATE 1
If I call the same interface fetchTasksWatchedByMeOfProject: in:
#pragma mark - NSFetchedResultsController Delegate
- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller
{
I will get 'two objects' as well.
UPDATE 2
I've tried:
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(ANY personWatchers == %@) AND (projectId == %d)", currentLoginUser, projectId];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(ANY personWatchers.personId == %@) AND (projectId == %d)", currentLoginUserId, projectId];
Still the same result.
UPDATE 3
I've checked the save:&error, error is nil.
解决方案 I've figured out this problem today with my teammates.
If you create a to-many relationship without inverse relationship, for example, Task has a to-many relationship watchers to Person, but Person doesn't have a inverse one to Task, then the relationship field watchers will be put in the Person table instead of a middle/mapping table.
Under this condition, my adding a Person p1 into the Task t1's watchers will update the watchers filed to 1 in the Person table.
Then, add Person p1 to the Task t2 as well, the watchers field will be update to 2 like below:
So, one Person can only point to one Task!
By adding a inverse relationship from Person to Task can walk around this problem.
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