Question

我正在尝试让RestKit和CoreData一起工作。我越来越近了，但是我收到了以下错误：

CoreData: error: Failed to call designated initializer on NSManagedObject class 'Book' 
*** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: 
    '[<Book 0x8454560> valueForUndefinedKey:]: the entity (null) is not key value coding-compliant for the key "title".'

在我看来，它正在成功找到我的Book类，并且它有一个title属性。我究竟做错了什么？

Books.xcdatamodel

Book
  title: String

我在localhost:3000/books/initial处有一个返回以下（JSON）

的网址

[{title:"one"}, {title:"two"}]

我正在使用mogenerator来创建我的课程。我没有向Book添加任何内容，但_Book显然已定义了title属性。

最后，这是我用来加载请求的代码。

RKObjectManager* objectManager = [RKObjectManager managerWithBaseURL:[NSURL URLWithString:@"http://localhost:3000/"]];
RKManagedObjectStore* objectStore = [[RKManagedObjectStore alloc] initWithManagedObjectModel:self.model];
objectManager.managedObjectStore = objectStore;

// Mappings
RKEntityMapping *bookMapping = [RKEntityMapping mappingForEntityForName:@"Book" inManagedObjectStore:objectStore];
[bookMapping addAttributeMappingsFromArray:@[@"title"]];

RKResponseDescriptor * responseDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:bookMapping pathPattern:@"books/initial/" keyPath:nil statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)];

[objectManager addResponseDescriptor:responseDescriptor];

// Send Request
[objectManager getObjectsAtPath:@"/books/initial/" parameters:nil success:^(RKObjectRequestOperation * operation, RKMappingResult *mappingResult) {
    NSLog(@"SUCCESS");
} failure: ^(RKObjectRequestOperation * operation, NSError * error) {
    NSLog(@"FAILURE %@", error);
}];

编辑：我在//Send Request应用的RKTwitterCoreData部分之前添加了以下几行，但我仍然遇到同样的错误

// Other Initialization (move this to app delegate)
[objectStore createPersistentStoreCoordinator];
[objectStore createManagedObjectContexts];

objectStore.managedObjectCache = [[RKInMemoryManagedObjectCache alloc] initWithManagedObjectContext:objectStore.persistentStoreManagedObjectContext];

Answer 1

问题是映射中的路径不正确。我有http://localhost:3000/作为我的域名，应该是http://localhost:3000，我有books/initial/作为应该/books/initial/的路径。

请参阅RestKit 0.20 — CoreData: error: Failed to call designated initializer on NSManagedObject class

我也忘了创建持久性商店。以下是完整的工作示例：

// Core Data Example
// Initialize RestKIT
RKObjectManager* objectManager = [RKObjectManager managerWithBaseURL:[NSURL URLWithString:@"http://localhost:3000"]];
RKManagedObjectStore* objectStore = [[RKManagedObjectStore alloc] initWithManagedObjectModel:self.model];
objectManager.managedObjectStore = objectStore;

// Mappings
RKEntityMapping *bookMapping = [RKEntityMapping mappingForEntityForName:@"Book" inManagedObjectStore:objectStore];
[bookMapping addAttributeMappingsFromArray:@[@"title"]];

RKResponseDescriptor * responseDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:bookMapping pathPattern:@"/books/initial/" keyPath:nil statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)];

[objectManager addResponseDescriptor:responseDescriptor];

// Other Initialization (move this to app delegate)
[objectStore createPersistentStoreCoordinator];

NSString *storePath = [RKApplicationDataDirectory() stringByAppendingPathComponent:@"RKTwitter.sqlite"];
NSString *seedPath = [[NSBundle mainBundle] pathForResource:@"RKSeedDatabase" ofType:@"sqlite"];
NSError *error;
NSPersistentStore *persistentStore = [objectStore addSQLitePersistentStoreAtPath:storePath fromSeedDatabaseAtPath:seedPath withConfiguration:nil options:nil error:&error];
NSAssert(persistentStore, @"Failed to add persistent store with error: %@", error);

[objectStore createManagedObjectContexts];

objectStore.managedObjectCache = [[RKInMemoryManagedObjectCache alloc] initWithManagedObjectContext:objectStore.persistentStoreManagedObjectContext];

// Send Request
[objectManager getObjectsAtPath:@"/books/initial/" parameters:nil success:^(RKObjectRequestOperation * operation, RKMappingResult *mappingResult) {
    NSLog(@"SUCCESS");
} failure: ^(RKObjectRequestOperation * operation, NSError * error) {
    NSLog(@"FAILURE %@", error);
}];

Answer 2

我没看到你在哪里添加了持久性商店。你忘记这样做了吗？

实体（null）不是密钥值编码兼容的密钥“标题”

2 个答案: