RestKit、NSFetchedResultsController 和删除孤立对象

Posted 2023-02-23

【中文标题】RestKit、NSFetchedResultsController 和删除孤立对象

【英文标题】：RestKit, NSFetchedResultsController, and deleting orphaned objects

【发布时间】：2013-12-23 15:37:02

【问题描述】：

我使用 NSFetchedResultsController 设置了 RestKit 并与 API 和核心数据正常工作，以显示信息。一切都运行良好，除了在服务器上删除本地对象后删除它们。我尝试按照 RestKit 文档使用 RKObjectManager 删除孤立对象，但它似乎不起作用。这就是我所拥有的，任何见解都会很棒：

对象映射

+ (RKMapping *)locationMapping
//Create object map
//Same mapping as object mapping, but to NSManagedObjects
RKEntityMapping *mapping = [RKEntityMapping mappingForEntityForName:@"Location" inManagedObjectStore:[RKManagedObjectStore defaultStore]];

//Map the identical json / object properties
[mapping addAttributeMappingsFromArray:@[@"name", @"city", @"zip", @"recipient", @"street", @"state"]];

//Map the non-identical properties (left side = json, right side = NSObject)
[mapping addAttributeMappingsFromDictionary:@
                                              @"id": @"locationID",
                                              @"user_id":@"userID"
                                              ];

[mapping setIdentificationAttributes:@[@"locationID"]];

[mapping addRelationshipMappingWithSourceKeyPath:@"user" mapping:[self userMapping]];
[mapping addConnectionForRelationship:@"user" connectedBy:@"userID"];

RKObjectManager *rkObjectManager = [RKObjectManager sharedManager];

//Delete any orphaned objects
[rkObjectManager addFetchRequestBlock:^NSFetchRequest *(NSURL *URL) 
    RKPathMatcher *pathMatcher = [RKPathMatcher pathMatcherWithPattern:@"/api/v1/:userID/locations"];
    NSDictionary *argsDict = nil;
    if ([pathMatcher matchesPath:[URL relativePath] tokenizeQueryStrings:NO parsedArguments:&argsDict]) 
        NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"Location"];
        return fetchRequest;
    
    return nil;
];


return mapping;

注意 - 运行映射或进行 API 调用时，addFetchRequestBlock 未执行

拉取数据

+(void)loadUserLocations
//Don't try to load if there is no logged in user
if(![self getCurrentUser])return;

//Create an index of successful status codes
NSIndexSet *statusCodeSet = RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful);

//Pull location mapping from Mapping Provider
RKMapping *mapping = [MappingProvider locationMapping];

//Determine how rest kit will deal with the response. Specific to API calls
RKResponseDescriptor *rkResponseDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:mapping
                                                                                          method:RKRequestMethodGET
                                                                                     pathPattern:@"/api/v1/users/:userID/locations"
                                                                                         keyPath:nil
                                                                                     statusCodes:statusCodeSet];

//Create the URL & response
NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:@"%@/users/%@/locations", [Statics baseURL], [self getCurrentUser].userID]];
NSURLRequest *request = [NSURLRequest requestWithURL:url];

//Create the operation. Pass through AFHttp (more options) or NSURL
//When the request hits the path pattern (in this case, /locations),
//it will use the mapping to create the appropriate items
RKManagedObjectRequestOperation *operation = [[RKManagedObjectRequestOperation alloc] initWithRequest:request responseDescriptors:@[rkResponseDescriptor]];


//Set the cache
operation.managedObjectCache = [RKManagedObjectStore defaultStore].managedObjectCache;
operation.managedObjectContext = [RKManagedObjectStore defaultStore].mainQueueManagedObjectContext;

[operation setCompletionBlockWithSuccess:^(RKObjectRequestOperation *operation, RKMappingResult *mappingResult) 

 failure:^(RKObjectRequestOperation *operation, NSError *error) 
    NSLog(@"Error: %@", error);
    NSLog(@"Response: %@", operation.HTTPRequestOperation.responseString);
];

[operation start];

设置 NSFetchedResultsController

-(NSFetchedResultsController*)fetchedResultsController
if (_fetchedResultsController != nil) 
    return _fetchedResultsController;


NSFetchRequest *fetchRequest =   [[RKManagedObjectStore defaultStore].managedObjectModel fetchRequestFromTemplateWithName:@"userLocations" substitutionVariables:@@"USERID":[User getCurrentUser].userID];

//Sort the request
NSSortDescriptor *sort = [[NSSortDescriptor alloc]
                          initWithKey:@"locationID" ascending:NO];
[fetchRequest setSortDescriptors:[NSArray arrayWithObject:sort]];

[fetchRequest setFetchBatchSize:20];

//Create a new controller and set it to the VC
self.fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest
                                                                    managedObjectContext:self.mainMOC sectionNameKeyPath:nil
                                                                               cacheName:@"Root"];
NSLog(@"%@",fetchRequest);

self.fetchedResultsController.delegate = self;

return self.fetchedResultsController;

这可能是缓存问题吗？还是我设置不当？

【参考方案1】：

您的 fetch 请求块中的路径模式 /api/v1/:userID/locations 与您的 GET 请求不匹配。

但您的主要问题是，要使用获取请求块，对象管理器需要运行请求。因为它是您显式创建请求和操作并执行。您应该完全创建和配置对象管理器并使用它来发出请求（这也应该是您编写的更少代码）。

【讨论】：

第一个问题：Doh！第二个问题：这很有意义。我并没有真正从示例中明确收集到这一点。谢谢！