核心數據錯誤消息

我創建了一個名爲「運動員」的核心數據實體。核心數據錯誤消息

這裏是我得到的錯誤：

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '+entityForName: nil is not a legal NSManagedObjectContext parameter searching for entity name 'Athlete''

這是在它打破了行：

Athlete *detail = [NSEntityDescription insertNewObjectForEntityForName:@"Athlete" inManagedObjectContext:context];

delegate.h

@property (readonly, strong, nonatomic) NSManagedObjectContext *managedObjectContext; 
@property (readonly, strong, nonatomic) NSManagedObjectModel *managedObjectModel; 
@property (readonly, strong, nonatomic) NSPersistentStoreCoordinator *persistentStoreCoordinator;

delegate.m

-(void)createData{ 

    NSManagedObjectContext *context = [self managedObjectContext]; 

    Athlete *detail = [NSEntityDescription insertNewObjectForEntityForName:@"Athlete" inManagedObjectContext:context]; 

    detail.first = @"Joe"; 

    detail.last = @"Pastrami"; 

    detail.phone = @"(123)456-7891"; 

    NSError *error; 

    if(![context save:&error]){ 
     NSLog(@"Error :("); 
    } 

    NSFetchRequest *request = [[NSFetchRequest alloc] init]; 

    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Athlete" inManagedObjectContext:context]; 

    [request setEntity:entity]; 

    NSArray *arr = [context executeFetchRequest:request error:&error]; 

    for (Athlete *ath in arr){ 
     NSLog(@"Name %@", ath.first); 
    } 

} 



- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions 
{ 
    [self createData]; 
}

來源

2013-07-22 Josue Espinosa

錯誤說明了一切：您的managedObjectContext爲零。

來源

2013-07-22 02:09:28

這就是那個東西。它不應該是零。我不知道它爲什麼這麼說。 –

@JosueEspinosa有時候事情並不像你認爲他們應該那樣工作。這就是堆棧跟蹤和調試有用的地方。跟蹤堆棧回到調用此方法的位置。做一些調試！ – borrrden

你可能想看斯坦福的CS193p視頻。老師向您演示如何使用UIManagedDocument設置Core Data存儲。一旦你明白它是如何建立的，這很簡單。 – Jamie

您是否正確地將您的managedObjectContext對象從AppDelegate傳遞到您的UIViewController？（在根與UINavigationController示例應用程序）

從 AppDelegate

：：如果沒有，2種方法來做到這一點

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { 
    NSManagedObjectContext *context = [self managedObjectContext]; 

    UINavigationController *navigationController = (UINavigationController *)self.window.rootViewController.navigationController; 
    YourViewController *yourViewController = (SearchViewController *)navigationController.topViewController; 
    yourViewController.managedObjectContext = self.managedObjectContext; 
    ... 
}

從YourViewController：

#import AppDelegate.h 
... 
@synthesize managedObjectContext; 

- (void)viewDidLoad 
    AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication]delegate]; 
    managedObjectContext = [appDelegate managedObjectContext]; 
    ... 
}

來源

2013-07-22 04:38:55 Yazid

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