使用 2 个类将对象映射到 CoreData

Posted 2023-03-13

【中文标题】使用 2 个类将对象映射到 CoreData

【英文标题】：Mapping an object to CoreData with 2 classes

【发布时间】：2014-09-25 21:08:12

【问题描述】：

所以这是我第一次尝试将对象映射到 CoreData，我认为我做对了，但我遇到的问题很少。首先，我只是不知道我是否以正确的方式映射它，第二个是我得到了成功响应但没有映射对象。

我有 2 个对象 DbRestError 和 DbRestCategory。 DbRestError 包含来自服务器的错误，而 DbRestCategory 包含类别本身。两者都从相同的响应中返回，但 RestKit 似乎无法映射它们。

这些是对象：

DbRestError

@interface DbRestError : NSManagedObject

@property (nonatomic, retain) NSNumber * statusCode;
@property (nonatomic, retain) NSString * errorTitle;

@end

DbRestCategory

@interface DbRestCategory : NSManagedObject

@property (nonatomic, retain) NSString * title;
@property (nonatomic, retain) NSNumber * idNum;

@end

这就是我使用 RestKit 初始化 CoreData 的方式：

- (void)setup

    self.objectStore = [[RKManagedObjectStore alloc] initWithManagedObjectModel:[self managedObjectModel]];

    NSString *path = [RKApplicationDataDirectory() stringByAppendingPathComponent:@"database.sqlite"];
    NSLog(@"Setting up store at %@", path);
    [self.objectStore addSQLitePersistentStoreAtPath:path
                              fromSeedDatabaseAtPath:nil
                                   withConfiguration:nil
                                             options:@ NSInferMappingModelAutomaticallyOption: @YES, NSMigratePersistentStoresAutomaticallyOption: @YES 
                                               error:nil];

    [self.objectStore createManagedObjectContexts];

这就是我初始化我的 RestKit 客户端的方式：

- (void)initRestClient

    NSURL *baseURL = [NSURL URLWithString:kWebServiceBaseURL];
    self.manager = [RKObjectManager managerWithBaseURL:baseURL];
    [self.manager setRequestSerializationMIMEType:RKMIMETypeJSON];
    [self.manager setAcceptHeaderWithMIMEType:RKMIMETypeJSON];
    [self.manager addResponseDescriptorsFromArray:[RKObjectManager sharedManager].responseDescriptors];
    [self.manager addRequestDescriptorsFromArray:[RKObjectManager sharedManager].requestDescriptors];
    [self.manager.HTTPClient.operationQueue setMaxConcurrentOperationCount:MAX_CONCURRENT_OPERATION_COUNT];
    [self.manager setManagedObjectStore:[[MainDb sharedDb] objectStore]];

    [RKObjectManager setSharedManager:self.manager];

    self.requestMethod = RKRequestMethodGET;
    self.statusCode = RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful);

    RKRoute *categoriesRoute = [RKRoute routeWithClass:[DbRestCategory class] pathPattern:kGetCategories method:self.requestMethod];
    categoriesRoute.shouldEscapePath = YES;
    [self.manager.router.routeSet addRoute:categoriesRoute];

    //  @@yosi -- Error Mapping
    //
    //
    RKEntityMapping *errorMapping = [RKEntityMapping mappingForEntityForName:@"DbRestError" inManagedObjectStore:[[MainDb sharedDb] objectStore]];
    [errorMapping addAttributeMappingsFromDictionary:@ @"statusCode" : @"statusCode", @"description" : @"errorTitle" ];

    //  @@yosi -- Categories Mapping
    //
    //
    RKEntityMapping *categoryMapping = [RKEntityMapping mappingForEntityForName:@"DbRestCategory" inManagedObjectStore:[[MainDb sharedDb] objectStore]];
    [categoryMapping addAttributeMappingsFromDictionary:@ @"id" : @"idNum", @"name" : @"title" ];

    RKObjectMapping *categoriesMapping = [RKObjectMapping mappingForClass:[RestCategories class]];
    [categoriesMapping addRelationshipMappingWithSourceKeyPath:@"categories" mapping:categoryMapping];
    [categoriesMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"error" toKeyPath:@"error" withMapping:errorMapping]];

    [[RKObjectManager sharedManager] addResponseDescriptor:[RKResponseDescriptor responseDescriptorWithMapping:categoriesMapping
                                                                                                        method:self.requestMethod
                                                                                                   pathPattern:kGetCategories
                                                                                                       keyPath:nil
                                                                                                   statusCodes:self.statusCode]];

这就是我自己处理请求的方式：

[[RKObjectManager sharedManager] getObject:[[DbRestCategory alloc] init] path:nil parameters:nil success:^(RKObjectRequestOperation *operation, RKMappingResult *mappingResult) 

 failure:^(RKObjectRequestOperation *operation, NSError *error) 

];

这是 JSON 的样子：

error: 
statusCode: 10,
description: "success"
,
categories: [
    
        id: "3",
    name: "cate 3"
    ,
    
        id: "4",
    name: "cate 4"
    ,
    
        id: "5",
    name: "cate 5"
    ,
    
        id: "1",
    name: "cate 1"
    ,
    
        id: "6",
    name: "cate 6"
    ,
    
        id: "2",
    name: "cate 2"
    
             ]

有人可以帮我理解为什么我得到一个没有任何对象的响应吗？

【问题讨论】：

error 和 categories 在相同的响应下。你为什么使用方法getObject 而不是getObjectsAtPath？您可以添加两个响应描述符映射两个实体。

@AnushaK 是的，我做到了，但仍然无法正常工作。现在我收到此错误：groups.google.com/forum/#!topic/restkit/2u5Ke_FnaZU

【参考方案1】：

试试这样的请求映射，

// Request Mapping

// Map error
RKEntityMapping *errorMapping = [RKEntityMapping mappingForEntityForName:@"DbRestError" inManagedObjectStore:[[MainDb sharedDb] objectStore]];
[errorMapping addAttributeMappingsFromDictionary:@ @"statusCode" : @"statusCode", @"description" : @"errorTitle" ];
[[RKObjectManager sharedManager] addResponseDescriptor:[RKResponseDescriptor responseDescriptorWithMapping:errorMapping method:self.requestMethod pathPattern:kGetCategories keyPath:@"error" statusCodes:self.statusCode]];

// Map Category
RKEntityMapping *categoryMapping = [RKEntityMapping mappingForEntityForName:@"DbRestCategory" inManagedObjectStore:[[MainDb sharedDb] objectStore]];
[categoryMapping addAttributeMappingsFromDictionary:@ @"id" : @"idNum", @"name" : @"title" ];

[[RKObjectManager sharedManager] addResponseDescriptor:[RKResponseDescriptor responseDescriptorWithMapping:categoriesMapping method:self.requestMethod pathPattern:kGetCategories keyPath:@"categories" statusCodes:self.statusCode]];