实体（空）不是关键字“标题”的关键值编码兼容的。 [英] The entity (null) is not key value coding-compliant for the key "title"

问题描述

我想让RestKit和CoreData一起工作。我越来越接近，但我得到以下错误：

I'm trying to get RestKit and CoreData to work together. I'm getting closer, but I'm getting the following error:

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，它找到我的Book类成功，它有一个title属性。我做错了什么？

It seems to me that it's finding my Book class successfully, and it DOES have a title property. What am I doing wrong?

Books.xcdatamodel

Books.xcdatamodel

Book
  title: String

我有一个URL

I have a url at localhost:3000/books/initial that returns the following (JSON)

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

我使用mogenerator类。我没有向 Book 添加任何内容，但是 _Book 显然已定义标题属性。

I'm using mogenerator to create my classes. I haven't added anything to Book, but _Book clearly has the title property defined.

最后，这里是我用来加载请求的代码。

Finally, here's the code I use to load the request.

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);
}];

---

EDIT：在 RKTwitterCoreData 应用程序中找到的 //发送请求部分之前添加了以下行，同样的错误

---

I added the following lines right before the //Send Request part, found in the RKTwitterCoreData app, but I still get the same error

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

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

推荐答案

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。

The problem was that path was not correct in the mapping. I had http://localhost:3000/ as my domain, where it should have been http://localhost:3000, and I had books/initial/ as the path where it should have been /books/initial/.

请参阅 RestKit 0.20 - CoreData：错误：无法调用NSManagedObject类上的指定初始化器

我也忘了创建持久存储。下面是完整的工作示例：

I also forgot to create the persistent store. Here's the full working example:

// 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);
}];

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