API滥用：尝试访问子上下文属性时尝试在非所有者协调器上序列化存储访问

Question

使用以下代码：

CustomObject *customObject = [[CustomObject alloc] initWithContext:self.persistentContainer.viewContext];
customObject.name = @"TEST";
customObject.customID = 1234;

NSManagedObjectContext *firstContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
firstContext.parentContext = self.persistentContainer.viewContext;
CustomObject *contextObj = [firstContext objectWithID:customObject.objectID];
NSError *error;

[self.persistentContainer.viewContext save:&error];
NSLog(@"ERROR [%@", error);
NSLog(@"NAME [%@]", contextObj.name);

我得到结果：

ERROR [(null)
[error] error:  API Misuse: Attempt to serialize store access on non-owning coordinator (PSC = 0x6000015fa300, store PSC = 0x0)
CoreData: error:  API Misuse: Attempt to serialize store access on non-owning coordinator (PSC = 0x6000015fa300, store PSC = 0x0)
NAME [(null)]

我试图理解为什么出现此警告。我希望在保存主上下文之后，我仍然能够在其子上下文上访问对象的属性，而不会出现任何问题。

有趣的部分是，如果我在保存主上下文之前取消对contextObj的操作，则一切正常：

CustomObject *customObject = [[CustomObject alloc] initWithContext:self.persistentContainer.viewContext];
customObject.name = @"TEST";
customObject.customID = 12234;

NSManagedObjectContext *firstContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
firstContext.parentContext = self.persistentContainer.viewContext;
CustomObject *contextObj = [firstContext objectWithID:customObject.objectID];
NSError *error;
NSLog(@"NAME [%@]", contextObj.name);
[self.persistentContainer.viewContext save:&error];
NSLog(@"ERROR [%@", error);
NSLog(@"NAME [%@]", contextObj.name);

NAME [TEST]
ERROR [(null)
NAME [TEST]

任何关于为什么发生这种情况的想法都将受到赞赏。 谢谢。