관리 대상 객체 컨텍스트가 애플리케이션 위임자가 아닌 경우

Question

코어 데이터에 대한 자습서를 수행 한 후이를 프로젝트에 적용하려고합니다. https://www.appcoda.com/introduction-to-core-data/

그래서 내가 통해 내 관리되는 개체 컨텍스트에 액세스하려고하면이 전무 같이

NSManagedObjectContext *context = [self context]; 

내가 널 예외 오류가 발생합니다. 여기보기 컨트롤러에 이전 컨텍스트를 정의

내가 AppDelegate에에서 만든 자동차입니다 ManagedObjectContext의 인스턴스를 얻을 것으로 판단

@interface UpdateCardsViewController() 

@property NSArray* fullCardList; 
@property NSManagedObjectContext* context; 

@end 

@implementation UpdateCardsViewController 

- (NSManagedObjectContext *) setManagedObjectContext { 
    NSManagedObjectContext *context = nil; 
    id delegate = [[UIApplication sharedApplication] delegate]; 
    if ([delegate respondsToSelector:@selector(managedObjectContext)]) { 
     context = [delegate managedObjectContext]; 
    } 
    return context; 
} 

. 문제가 넣다

여기에 또한 내 AppDelegate에 있습니다 : 내가 접근 할 수있다

#import "AppDelegate.h" 

@interface AppDelegate() 

@end 

@implementation AppDelegate 


- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { 
    // Override point for customization after application launch. 
    UITabBarController *tabBar = (UITabBarController *)self.window.rootViewController; 
    tabBar.selectedIndex = 2; 
    return YES; 
} 


- (void)applicationWillResignActive:(UIApplication *)application { 
    // Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state. 
    // Use this method to pause ongoing tasks, disable timers, and invalidate graphics rendering callbacks. Games should use this method to pause the game. 
} 


- (void)applicationDidEnterBackground:(UIApplication *)application { 
    // Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later. 
    // If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits. 
} 


- (void)applicationWillEnterForeground:(UIApplication *)application { 
    // Called as part of the transition from the background to the active state; here you can undo many of the changes made on entering the background. 
} 


- (void)applicationDidBecomeActive:(UIApplication *)application { 
    // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface. 
} 


- (void)applicationWillTerminate:(UIApplication *)application { 
    // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:. 
    // Saves changes in the application's managed object context before the application terminates. 
    [self saveContext]; 
} 

#pragma mark - Core Data stack 

@synthesize persistentContainer = _persistentContainer; 

- (NSPersistentContainer *)persistentContainer { 
    // The persistent container for the application. This implementation creates and returns a container, having loaded the store for the application to it. 
    @synchronized (self) { 
     if (_persistentContainer == nil) { 
      _persistentContainer = [[NSPersistentContainer alloc] initWithName:@"Lifepoints"]; 
      [_persistentContainer loadPersistentStoresWithCompletionHandler:^(NSPersistentStoreDescription *storeDescription, NSError *error) { 
       if (error != nil) { 
        // Replace this implementation with code to handle the error appropriately. 
        // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. 

        /* 
        Typical reasons for an error here include: 
        * The parent directory does not exist, cannot be created, or disallows writing. 
        * The persistent store is not accessible, due to permissions or data protection when the device is locked. 
        * The device is out of space. 
        * The store could not be migrated to the current model version. 
        Check the error message to determine what the actual problem was. 
        */ 
        NSLog(@"Unresolved error %@, %@", error, error.userInfo); 
        abort(); 
       } 
      }]; 
     } 
    } 

    return _persistentContainer; 
} 

#pragma mark - Core Data Saving support 

- (void)saveContext { 
    NSManagedObjectContext *context = self.persistentContainer.viewContext; 
    NSError *error = nil; 
    if ([context hasChanges] && ![context save:&error]) { 
     // Replace this implementation with code to handle the error appropriately. 
     // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. 
     NSLog(@"Unresolved error %@, %@", error, error.userInfo); 
     abort(); 
    } 
} 


@end 

이 완전히 잘못,하지만 난가이 시점까지 튜토리얼을 가지고 생각했다.

감사합니다.

Answer 1

링크 된 자습서는 구식이지만 (iOS10 이전) iOS10 + 코어 데이터 스택을 사용하고 있습니다. 당신이 명확하게 코어 데이터 스택 AppDelegate에 존재하는 것을 알고 있기 때문에

이

- (NSManagedObjectContext *) managedObjectContext { 
    AppDelegate *delegate = (AppDelegate *)[[UIApplication sharedApplication] delegate]; 
    return [delegate persistentContainer.viewContext]; 
} 

respondsSelector 검사에 방법을 변경

필요가 없습니다. 그리고 당신은 문맥이 get이 아니기 때문에 set 팅입니다.

context 중 하나 필요하지 않은 속성, 단지 쓰기

NSManagedObjectContext *context = [self managedObjectContext];