RestKit本地删除对象，依然出现在mapping中

Posted 2023-03-05

【中文标题】RestKit本地删除对象，依然出现在mapping中

【英文标题】：RestKit local deletion of objects, still appears in mapping

【发布时间】：2014-03-27 08:30:40

【问题描述】：

我正在为我的应用程序使用 RestKit 0.20.3。它具有离线模式，所以我必须将对象存储在本地核心数据中。

每当从服务器中删除某些对象时，它都会以 JSON 格式发送deleted = true 属性，我在与deletionPredicate 的映射中处理该属性。 这是我的地图。

- (RKEntityMapping *)meetingsMapping 

    RKEntityMapping *meetingsMapping = [RKEntityMapping mappingForEntityForName:@"DBMeetings" inManagedObjectStore:objectManager.managedObjectStore];
    meetingsMapping.setDefaultValueForMissingAttributes = NO;
    meetingsMapping.deletionPredicate = [NSPredicate predicateWithFormat:@"shouldBeDeleted = 1"];
    [meetingsMapping setModificationAttributeForName:@"updated_at"];
    meetingsMapping.identificationAttributes = @[@"id"];

    [meetingsMapping addAttributeMappingsFromDictionary:@
                                                      @"id": @"id",
                                                      @"title": @"title",

                                                      @"start_date_human": @"start_date_human",
                                                      @"start_time_human": @"start_time_human",
                                                      @"finish_date_human": @"finish_date_human",
                                                      @"finish_time_human": @"finish_time_human",

                                                      @"lock": @"lock",
                                                      @"location": @"location",
                                                      @"sample": @"sample",

                                                      @"deleted": @"shouldBeDeleted",

                                                      @"created_at": @"created_at",
                                                      @"updated_at": @"updated_at",
                                                      @"follow_up_id": @"follow_up_id",
                                                      @"total_topics": @"total_topics",
                                                      ];

[meetingsMapping addRelationshipMappingWithSourceKeyPath:@"tags" mapping:[self tagsMapping]];
[meetingsMapping addRelationshipMappingWithSourceKeyPath:@"required_participants" mapping:[self contactsMapping]];
[meetingsMapping addRelationshipMappingWithSourceKeyPath:@"optional_participants" mapping:[self contactsMapping]];
[meetingsMapping addRelationshipMappingWithSourceKeyPath:@"readonly_participants" mapping:[self contactsMapping]];
[meetingsMapping addRelationshipMappingWithSourceKeyPath:@"organizer" mapping:[self contactsMapping]];

return meetingsMapping;

它运行良好，并且从本地 CoreData 中删除了属性。

问题是getObjectsAtPath 方法仍然返回mappingResult 参数中的所有对象。

[[RKObjectManager sharedManager] getObjectsAtPath:[NSString stringWithFormat:@"%@?type=past&page=%i", URL_MEETINGS, pageNo]
                                       parameters:nil
                                          success:^(RKObjectRequestOperation *operation, RKMappingResult *mappingResult) 
                                              KLog(@"%@", mappingResult.array); // It is returning all objects, not only non-deleted objects 
                                              completionHandler(mappingResult.array, nil);
                                          
                                          failure:^(RKObjectRequestOperation *operation, NSError *error) 
                                              completionHandler(nil, error);
                                          ];   

假设如果删除了 20 个对象中的 5 个，mappingResult.array 返回 20 条记录而不是 15 条。这 5 条删除的记录没有数据。当我登录mappingResult.array时，前5条记录打印如下：

2014-03-27 13:10:14.105 MeetingKing[7851:70b] W restkit.network.core_data:RKManagedObjectRequestOperation.m:125 Unable to refetch managed object <DBMeetings: 0xc1cb820> (entity: DBMeetings; id: 0xc1a6a60 <x-coredata://7B9FC7F6-C0E9-4DF5-91AC-D7C49F54B4F5/DBMeetings/t2915CF2E-2D7D-4E29-8B39-B1C51151809410> ; data: <fault>): the object has a temporary managed object ID.
2014-03-27 13:10:14.105 MeetingKing[7851:70b] W restkit.network.core_data:RKManagedObjectRequestOperation.m:125 Unable to refetch managed object <DBMeetings: 0xc5b2ed0> (entity: DBMeetings; id: 0xc5d1110 <x-coredata://7B9FC7F6-C0E9-4DF5-91AC-D7C49F54B4F5/DBMeetings/t2915CF2E-2D7D-4E29-8B39-B1C51151809416> ; data: <fault>): the object has a temporary managed object ID.
2014-03-27 13:10:14.106 MeetingKing[7851:70b] W restkit.network.core_data:RKManagedObjectRequestOperation.m:125 Unable to refetch managed object <DBMeetings: 0xc58b6a0> (entity: DBMeetings; id: 0xc5d3de0 <x-coredata://7B9FC7F6-C0E9-4DF5-91AC-D7C49F54B4F5/DBMeetings/t2915CF2E-2D7D-4E29-8B39-B1C51151809417> ; data: <fault>): the object has a temporary managed object ID.
2014-03-27 13:10:14.106 MeetingKing[7851:70b] W restkit.network.core_data:RKManagedObjectRequestOperation.m:125 Unable to refetch managed object <DBMeetings: 0xc5b50e0> (entity: DBMeetings; id: 0xc5d4af0 <x-coredata://7B9FC7F6-C0E9-4DF5-91AC-D7C49F54B4F5/DBMeetings/t2915CF2E-2D7D-4E29-8B39-B1C51151809419> ; data: <fault>): the object has a temporary managed object ID.
2014-03-27 13:10:14.107 MeetingKing[7851:70b] W restkit.network.core_data:RKManagedObjectRequestOperation.m:125 Unable to refetch managed object <DBMeetings: 0xc1ed5a0> (entity: DBMeetings; id: 0xc1c84e0 <x-coredata://7B9FC7F6-C0E9-4DF5-91AC-D7C49F54B4F5/DBMeetings/t2915CF2E-2D7D-4E29-8B39-B1C51151809422> ; data: <fault>): the object has a temporary managed object ID.

如果我签入数据库，则只有 15 条记录。没关系。

如果我明确地从数据库中获取，它只返回 15 条记录，没关系

但是在getObjectsAtPath回调中，mappingResult.array参数返回20条记录。那不行。 :(

问题是mappingResult.array的count变成了20，而我的UITableView显示20行，其中5行没有数据。

RestKit 是否有任何其他回调可以准确返回 15 条记录，这样我就不必从数据库中显式获取记录？

【参考方案1】：

mappingResult 正在返回映射的对象，这是它应该做的。一些项目随后被删除的事实并没有改变这一点 - 实际上，您拥有所需的所有信息，因为您知道所有已映射的对象以及哪些对象因此被删除。

简单的解决方案是使用NSFetchedResultsController 来获取表格视图的数据。它将正确处理更新、插入和删除，您不需要做额外的工作。

或者，您需要迭代 mappingResult.array 并过滤掉已删除的项目。最好的验证方法是使用支票：

if (item.isDeleted || item.managedObjectContext == nil) 
    // remove the now invalid item...

【讨论】：

感谢@wain，我正在使用 MagicalRecords，并用它再次从数据库中获取数据。它正在返回正确的记录。我想知道是否有其他方法可以实现这一目标。