iPhone核心数据错误

Question

我的AppDelegate.h：

#import <UIKit/UIKit.h>
#import "Child.h"

@interface AppDelegate : UIResponder <UIApplicationDelegate> {
    NSManagedObjectModel *managedObjectModel;
    NSManagedObjectContext *managedObjectContext;
    NSPersistentStoreCoordinator *persistentStoreCoordinator;
}
@property (readonly, strong, nonatomic) NSManagedObjectContext *managedObjectContext;
@property (readonly, retain, nonatomic) NSManagedObjectModel *managedObjectModel;
@property (readonly, strong, nonatomic) NSPersistentStoreCoordinator *persistentStoreCoordinator;
- (NSString *)applicationDocumentsDirectory;
@property (strong, nonatomic) UIWindow *window;
@end

AppDelegate.m:

#import "AppDelegate.h"
@implementation AppDelegate

@synthesize managedObjectContext = __managedObjectContext;
@synthesize managedObjectModel = __managedObjectModel;
@synthesize persistentStoreCoordinator = __persistentStoreCoordinator;
@synthesize window = _window;

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.
    NSManagedObjectContext *context = [self managedObjectContext];
    if (!context) {
        NSLog(@"Error");
    }
    return YES;
}
- (void)applicationWillTerminate:(UIApplication *)application { /* Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:. */
    NSError *error;
    if (managedObjectContext != nil) {
        if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error]) {
        // Handle the error.
        } 
    }
}
// Explicitly write Core Data accessors
- (NSManagedObjectContext *) managedObjectContext {
    if (managedObjectContext != nil) {
        return managedObjectContext;
    }
    NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
    if (coordinator != nil) {
        managedObjectContext = [[NSManagedObjectContext alloc] init];
        [managedObjectContext setPersistentStoreCoordinator: coordinator];
    }
    return managedObjectContext;
}
- (NSManagedObjectModel *)managedObjectModel {
    if (managedObjectModel != nil) {
        return managedObjectModel;
    }
    managedObjectModel = [NSManagedObjectModel mergedModelFromBundles:nil];
    return managedObjectModel;
}
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {
    if (persistentStoreCoordinator != nil) {
        return persistentStoreCoordinator;
    }
    NSURL *storeUrl = [NSURL fileURLWithPath: [[self applicationDocumentsDirectory] stringByAppendingPathComponent: @"iSalahProject.sqlite"]];
    NSError *error = nil;
    persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
    if(![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeUrl options:nil error:&error]) {
        /*Error for store creation should be handled in here*/
    }
    return persistentStoreCoordinator;
}
- (NSString *)applicationDocumentsDirectory {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *basePath = ([paths count] > 0) ? [paths objectAtIndex:0] : nil;
    return basePath;
}
@end

我的控制器实现类正在创建实体，我收到错误：

-(IBAction)addChildren:(id)sender{
    inputChildName = nameOfChild.text;
    NSManagedObjectContext *context = [app managedObjectContext];
    Child * childrenName = [NSEntityDescription insertNewObjectForEntityForName:@"Child" inManagedObjectContext:context];
    childrenName.name = inputChildName;
}

我得到的错误是：

*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '+entityForName: could not locate an NSManagedObjectModel for entity name 'Child''

我正在使用 iOS-5 XCode 4.2 ARC。请帮我解决这个问题，我已经花了几个小时解决它，但我找不到任何解决方案。

Answer 1

您的应用程序正在终止，因为您的 managedObjectContext 为 nil。检查它，如果它的 nil 从委托复制它。您可以在 -(IBAction)addChildren:(id)sender 方法中使用此 if 条件

if (managedObjectContext == nil) 
{ 
    managedObjectContext = [(CoreDataBooksAppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext]; 
    NSLog(@"After managedObjectContext: %@",  managedObjectContext);
}

Answer 2

以下是发生此错误的可能性：

• 实体名称中的错字。
• Nil 托管对象上下文对象。
• 未能将包含实体的模型添加到持久化 存储上下文使用。
• 未能将正确的持久存储添加到上下文本身。