objective-c - 核心数据唯一性不起作用？

Question

当使用两个托管对象上下文时，我在处理单个上下文中同一实体的重复对象时遇到问题。

考虑以下代码:

[childMOC performBlockAndWait:^{

    // CREATE PERSON IN CHILD MOC
    Person *person = [NSEntityDescription insertNewObjectForEntityForName:@"Person" 
                                                   inManagedObjectContext:childMOC];

    person.name = @"Ben";

    // SAVE CHILD MOC TO PUSH CHANGES TO MAIN MOC
    [childMOC save:nil];

    NSManagedObjectID *personID = person.objectID;

    [mainMOC performBlockAndWait:^{
        // SAVE MAIN MOC TO PERSIST THE PERSON AND REPLACE ID TO PERMANENT
        [mainMOC save:nil];

        // GET THE PERSON IN THE MAIN MOC
        Person *personInMainContext = (Person*)[mainMOC objectWithID:personID];

        // GET THE PERSON'S NEW PERMANENT ID
        NSManagedObjectID *personIdAfterSaveToPersistentStore = personInMainContext.objectID;

        [childMOC performBlockAndWait:^{

            // GET THE PERSON IN THE CHILD MOC WITH ITS NEW PERMANENT ID
            // (this is common when sending the id from mainMOC to childMOC)
            Person *samePersonFetchedFresh = (Person*)[childMOC objectWithID:personIdAfterSaveToPersistentStore];

            // THE PERSON OBJECTS SHOULD BE EXACTLY THE SAME BECAUSE THE MOC GUARANTEES UNIQUING
            samePersonFetchedFresh.name = @"Jerry";
            NSLog(@"%@ & %@", person.name, samePersonFetchedFresh.name);

            // OUTPUT: Ben & Jerry
            // NOT THE SAME?!
        }];
    }];
}];

这意味着在子 MOC 中创建的对象在保存在主 MOC/持久存储中时会失去其唯一性。

谁能解释为什么 uniquing 在这种情况下不起作用？

Answer 1

在记录名字之前尝试刷新你的人物。我认为 uniquing 有效，但缓存失效可能无效。