Question

我创建了一个名为：＆＃34;运动员＆＃34;。

的核心数据实体

以下是我收到的错误：

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

这是它破裂的地方：

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];
}

Answer 1

错误说明了一切：您的managedObjectContext为零。

Answer 2

您是否已将managedObjectContext对象从AppDelegate正确传递到UIViewController？如果没有，有两种方法可以做到这一点：

来自AppDelegate（示例应用，根目录为UINavigationController）：

- (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;
    ...
}

来自YourViewController：

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

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

核心数据错误消息

2 个答案: