我正在研究我的文凭项目，其中包括一个带有核心数据数据库的 iOS 客户端和一个 Ruby on Rails 服务器。我正在使用 RestKit 进行它们之间的通信。目前我在让整个系统正常工作时遇到了一个大问题:当我尝试将响应映射到来自服务器的对象时，我得到了以下异常:
2013-02-08 22:40:43.947 App[66735:5903] *** Assertion failure in -[RKManagedObjectResponseMapperOperation performMappingWithObject:error:], ~/Repositories/App/RestKit/Code/Network/RKResponseMapperOperation.m:358
2013-02-08 23:04:30.562 App[66735:5903] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Unable to perform mapping: No `managedObjectContext` assigned. (Mapping response.URL = http://localhost:3000/contacts?auth_token=s78UFMq8mCQrr12GZcyx)'
*** First throw call stack:
(0x1de9012 0x1c0ee7e 0x1de8e78 0x16a4f35 0x8f56e 0x8d520 0x1647d23 0x1647a34 0x16d4301 0x23a253f 0x23b4014 0x23a52e8 0x23a5450 0x90ac6e12 0x90aaecca)
libc++abi.dylib: terminate called throwing an exception
我正在尝试从服务器加载一个联系人列表(一个数组)，它应该在核心数据中保存为“用户”。
我已经在数据模型类 中构建了我所有的核心数据代码，就像我在这个视频中看到的那样:http://nsscreencast.com/episodes/11-core-data-basics .在这里:
头文件:
#import <Foundation/Foundation.h>
#import <CoreData/CoreData.h>
@interface AppDataModel : NSObject
+ (id)sharedDataModel;
@property (nonatomic, readonly) NSManagedObjectContext *mainContext;
@property (nonatomic, strong) NSManagedObjectModel *managedObjectModel;
@property (nonatomic, readonly) NSPersistentStoreCoordinator *persistentStoreCoordinator;
- (NSString *)modelName;
- (NSString *)pathToModel;
- (NSString *)storeFilename;
- (NSString *)pathToLocalStore;
@end
执行文件:
#import "AppDataModel.h"
@interface AppDataModel ()
- (NSString *)documentsDirectory;
@end
@implementation AppDataModel
@synthesize managedObjectModel = _managedObjectModel;
@synthesize persistentStoreCoordinator = _persistentStoreCoordinator;
@synthesize mainContext = _mainContext;
+ (id)sharedDataModel {
static AppDataModel *__instance = nil;
if (__instance == nil) {
__instance = [[AppDataModel alloc] init];
}
return __instance;
}
- (NSString *)modelName {
return @"AppModels";
}
- (NSString *)pathToModel {
return [[NSBundle mainBundle] pathForResource:[self modelName]
ofType:@"momd"];
}
- (NSString *)storeFilename {
return [[self modelName] stringByAppendingPathExtension:@"sqlite"];
}
- (NSString *)pathToLocalStore {
return [[self documentsDirectory] stringByAppendingPathComponent:[self storeFilename]];
}
- (NSString *)documentsDirectory {
NSString *documentsDirectory = nil;
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
documentsDirectory = [paths objectAtIndex:0];
return documentsDirectory;
}
- (NSManagedObjectContext *)mainContext {
if (_mainContext == nil) {
_mainContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
_mainContext.persistentStoreCoordinator = [self persistentStoreCoordinator];
}
return _mainContext;
}
- (NSManagedObjectModel *)managedObjectModel {
if (_managedObjectModel == nil) {
NSURL *storeURL = [NSURL fileURLWithPath:[self pathToModel]];
_managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:storeURL];
}
return _managedObjectModel;
}
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {
if (_persistentStoreCoordinator == nil) {
NSLog(@"SQLITE STORE PATH: %@", [self pathToLocalStore]);
NSURL *storeURL = [NSURL fileURLWithPath:[self pathToLocalStore]];
NSPersistentStoreCoordinator *psc = [[NSPersistentStoreCoordinator alloc]
initWithManagedObjectModel:[self managedObjectModel]];
NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
[NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];
NSError *e = nil;
if (![psc addPersistentStoreWithType:NSSQLiteStoreType
configuration:nil
URL:storeURL
options:options
error:&e]) {
NSDictionary *userInfo = [NSDictionary dictionaryWithObject:e forKey:NSUnderlyingErrorKey];
NSString *reason = @"Could not create persistent store.";
NSException *exc = [NSException exceptionWithName:NSInternalInconsistencyException
reason:reason
userInfo:userInfo];
@throw exc;
}
_persistentStoreCoordinator = psc;
}
return _persistentStoreCoordinator;
}
@end
User 类 非常简单，使用 xCode 自动生成。
头文件:
#import <Foundation/Foundation.h>
#import <CoreData/CoreData.h>
@interface User : NSManagedObject
@property (nonatomic, retain) NSString * email;
@property (nonatomic, retain) NSString * firstName;
@property (nonatomic, retain) NSString * lastName;
@property (nonatomic, retain) NSNumber * userID;
@end
执行文件:
#import "User.h"
@implementation User
@dynamic email;
@dynamic firstName;
@dynamic lastName;
@dynamic userID;
@end
就像数据模型类一样，我有一个用于通信的服务器管理器类:
头文件:
#import <Foundation/Foundation.h>
#import <RestKit/RestKit.h>
#import "AppServerProtocol.h"
#import "AppDataModel.h"
@interface AppServer : NSObject <AppServerDelegate>
+ (id)sharedInstance;
@property (strong, nonatomic) RKObjectManager *objectManager;
@property (strong, nonatomic) RKEntityMapping *userMapping;
@end
和实现文件:
#import "AppServer.h"
#import "User.h"
#import "Device.h"
#import "Ping.h"
#import "AppAppDelegate.h"
@interface AppServer ()
@property BOOL initialized;
@end
@implementation AppServer
+ (id)sharedInstance {
static AppServer *__instance = nil;
if (__instance == nil) {
__instance = [[AppServer alloc] init];
__instance.initialized = NO;
}
if (![__instance initialized]) {
[__instance initServer];
}
return __instance;
}
- (void)initServer {
// initialize RestKit
NSURL *baseURL = [NSURL URLWithString:@"http://localhost:3000"];
_objectManager = [RKObjectManager managerWithBaseURL:baseURL];
// enable activity indicator spinner
[AFNetworkActivityIndicatorManager sharedManager].enabled = YES;
// initialize managed object store
_objectManager.managedObjectStore = [[RKManagedObjectStore alloc] initWithManagedObjectModel:[[AppDataModel sharedDataModel] managedObjectModel]];
_userMapping = [RKEntityMapping mappingForEntityForName:@"User" inManagedObjectStore:_objectManager.managedObjectStore];
[_userMapping addAttributeMappingsFromDictionary:@{
@"email" : @"email",
@"firstName" : @"first_name",
@"lastName" : @"last_name"
}];
[_userMapping setIdentificationAttributes: @[@"userID"]];
RKResponseDescriptor *contactsResponseDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:_userMapping pathPattern:@"/contacts" keyPath:nil statusCodes:nil];
[_objectManager addResponseDescriptor:contactsResponseDescriptor];
_initialized = YES;
}
// contacts
- (void)getContactsForCurrentUser {
NSString *authToken = [[NSUserDefaults standardUserDefaults] objectForKey:@"AppAuthenticationToken"];
[_objectManager getObjectsAtPath:@"/contacts" parameters:@{@"auth_token": authToken} success:^(RKObjectRequestOperation *operation, RKMappingResult *mappingResult) {
RKLogInfo(@"Load collection of contacts: %@", mappingResult.array);
} failure:^(RKObjectRequestOperation *operation, NSError *error) {
RKLogError(@"Operation failed with error: %@", error);
}];
}
@end
所以当我打开联系人 TableView 时，它被正确设置为使用获取的结果 Controller (成功地将实体从数据库中拉出)，我有一个危险的刷新按钮，它调用方法 你刚刚阅读了上面的内容:
- (void)downloadContacts {
[[AppServer sharedInstance] getContactsForCurrentUser];
}
这是响应的格式:
[
{
"created_at":"2013-01-11T14:03:57Z",
"email":"john@example.com",
"first_name":"John",
"id":2,
"last_name":"Doe",
"updated_at":"2013-02-07T10:57:16Z"
},
{
"created_at":"2013-01-11T14:03:57Z",
"email":"jane@example.com",
"first_name":"Jane",
"id":3,
"last_name":"Doe",
"updated_at":"2013-02-07T10:57:16Z"
}
]
在异常发生之前控制台声明如下:
2013-02-08 22:40:36.892 App[66735:c07] I restkit:RKLog.m:34 RestKit logging initialized...
2013-02-08 22:40:36.994 App[66735:c07] SQLITE STORE PATH: ~/Library/Application Support/iPhone Simulator/6.0/Applications/D735548F-DF42-4E13-A7EF-53DF0C5D8F3B/Documents/AppModels.sqlite
2013-02-08 22:40:37.001 App[66735:c07] Context is ready!
2013-02-08 22:40:43.920 App[66735:c07] I restkit.network:RKHTTPRequestOperation.m:154 GET 'http://localhost:3000/contacts?auth_token=s78UFMq8mCQrr12GZcyx'
2013-02-08 22:40:43.945 App[66735:c07] I restkit.network:RKHTTPRequestOperation.m:181
RestKit 库的行，在抛出整个异常之前失败的是:
NSAssert(self.managedObjectContext, @"Unable to perform mapping: No `managedObjectContext` assigned. (Mapping response.URL = %@)", self.response.URL);
我已经回到了 AppServer.m 文件中的 initServer 方法，其中，在方法返回之前，RKObjectManager 类的属性是这样的:http://imgur.com/LM5ZU9m
正如我所调试的那样，我发现问题不在于服务器端或应用程序的通信 - 我可以看到 JSON 已接收并反序列化为一个数组，但在它传递给下一个方法的那一刻应该将它保存到 Core Data，由于托管对象上下文的 NSAssert，整个应用程序变得一团糟。
非常感谢任何帮助!
最佳答案
经过几天的调试，我终于找到了问题所在:看起来我还必须设置本地持久性存储的路径并为托管对象存储自己生成托管对象上下文。
这是我找到解决方案的地方:https://github.com/RestKit/RestKit/issues/1221#issuecomment-13327693
我刚刚在我的服务器初始化方法中添加了几行:
NSError *error = nil;
NSString *pathToPSC = [[AppDataModel sharedDataModel] pathToLocalStore];
_objectManager.managedObjectStore = [[RKManagedObjectStore alloc] initWithManagedObjectModel:[[AppDataModel sharedDataModel] managedObjectModel]];
[_objectManager.managedObjectStore addSQLitePersistentStoreAtPath:pathToPSC fromSeedDatabaseAtPath:nil withConfiguration:nil options:nil error:&error];
if (error != nil) {
NSLog(@"\nSerious object store error!\n");
return;
} else {
[_objectManager.managedObjectStore createManagedObjectContexts];
}
关于ios - RestKit 崩溃是因为 NSManagedObjectContext 在 RKResponseMapperOperation 中为 nil，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/14781910/