ios - 实体 (null) 与键 "title"的键值编码不兼容

Question

我正在尝试让 RestKit 和 CoreData 协同工作。我越来越近了，但出现以下错误:

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，它成功地找到了我的 Book 类，并且它确实有一个 title 属性。我究竟做错了什么？

---

Books.xcdatamodel

Book
  title: String

我在 localhost:3000/books/initial 有一个 url，返回以下 (JSON)

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

我正在使用 mogenerator 创建我的类。我没有向 Book 添加任何内容，但是 _Book 显然定义了 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 部分之前添加了以下几行，可在 RKTwitterCoreData 应用程序中找到，但我仍然得到同样的错误

// 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，它应该是 http://localhost:3000，我有 books/initial/ 作为它应该是 /books/initial/ 的路径。

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

我也忘了创建持久存储。这是完整的工作示例:

// 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);
}];