如何在具有相同值的Core Data中保存对象？

Question

我将核心数据中的对象保存为以下格式。

    {
        "propertyId": 1,
        "name": "some_name_1",
        "userName": "some_email_1"
    },
    {
        "propertyId": 1,
        "name": "some_name_2",
        "userName": "some_email_2"
    },
    {
        "propertyId": 2,
        "name": "some_name_3",
        "userName": "some_email_3"
    },
    {
        "propertyId": 2,
        "name": "some_name_4",
        "userName": "some_email_4"
    },
    {
        "propertyId": 3,
        "name": "some_name_5",
        "userName": "some_email_5"
    },
    {
        "propertyId": 3,
        "name": "some_name6_",
        "userName": "some_email_6"
    }

现在，问题是只有同一propertyId组中的最后一个对象才会保存在Core Data中。

这是我从之前的开发人员那里得到的代码。映射用于存储数据。

RKEntityMapping *rkEntityMapping = [RKEntityMapping mappingForEntityForName:@"PropertyAssignee" inManagedObjectStore:self.managedObjectStore];
rkEntityMapping.identificationAttributes = @[@"propertyId"];

[rkEntityMapping addAttributeMappingsFromDictionary:@{
                                                      @"propertyId": @"propertyId",
                                                      @"name": @"name",
                                                      @"userName": @"userName"}];

[rkEntityMapping addConnectionForRelationship:@"property" connectedBy:@{@"propertyId": @"objId"}];

RKObjectMapping *syncMapping = [RKObjectMapping mappingForClass:[NSMutableDictionary class]];

[syncMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"propertyAssgineeResponse" toKeyPath:@"propertyAssgineeResponse" withMapping:propertAssigneeMapping]];

RKResponseDescriptor *responseDescriptorProperties = [RKResponseDescriptor responseDescriptorWithMapping:syncMapping method:RKRequestMethodAny pathPattern:@"/api/sync" keyPath:nil statusCodes:[NSIndexSet indexSetWithIndex:200]];

[self.objectManager addResponseDescriptor:responseDescriptorProperties];

我不知道为什么会发生这种情况。