1

我正在尝试重置使用 Core Data 的应用程序，为此，我编写了下面的代码

- (void) resetApplicationModel
{
//    NSError *error;
    NSError *error;
    // retrieve the store URL
    NSURL * storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"abc.sqlite"];
    // lock the current context
    [self.managedObjectContext lock];

   [self.managedObjectContext reset];//to drop pending changes
    //delete the store from the current managedObjectContext
    if ([[self.managedObjectContext persistentStoreCoordinator] removePersistentStore:[[[self.managedObjectContext persistentStoreCoordinator] persistentStores] lastObject] error:&error])
    {
        // remove the file containing the data
        if([[NSFileManager defaultManager] removeItemAtURL:storeURL error:&error])
        {
            //recreate the store like in the appDelegate method
            if([[self.managedObjectContext persistentStoreCoordinator] addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error] == nil)
            {
                NSLog( @"could not create new persistent store at %@ - %@", [storeURL absoluteString], [error localizedDescription]);
            }
        }
        else
        {
            NSLog( @"could not remove the store URL at %@ - %@", [storeURL absoluteString], [error localizedDescription]);
        }

    }
    else
    {
        NSLog( @"could not remove persistent store - %@", [error localizedDescription]);
    }
    [self.managedObjectContext unlock];

      __managedObjectContext = nil;

    [self managedObjectContext];

    _rootViewController.controller = nil;//Make NSFetchResultsController nil;

}

此代码在 ios 6.1 模拟器上运行良好，没有问题，但是当我在运行 iOS 6.1.3 的 iphone 4 上检查此代码时，持久性文件没有被删除，我收到错误消息

“无法删除文件中的商店 URL：//localhost/var/mobile/Applications/147E198E-FAB9-46EA-BE4B-4411AFA013FB/Documents/abc.sqlite - 操作无法完成。（Cocoa 错误 4。） "

但是所有数据都被删除了，现在当我尝试在 coreData 中添加新数据时，我收到一条错误消息

“由于未捕获的异常‘NSInternalInconsistencyException’而终止应用程序，原因：‘此 NSPersistentStoreCoordinator 没有持久存储。它无法执行保存操作。’”

请帮帮我

问候兰吉特

4

1 回答 1

1

在 NSManagedObjectContext 上创建一个类别，然后实现：

- (BOOL)deleteAllObjectsForEntityName:(NSString *)entity withError:(NSError *__autoreleasing *)error {

NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:[NSEntityDescription entityForName:entity inManagedObjectContext:self]];
[request setIncludesPropertyValues:NO];

NSArray *allObjects = [self executeFetchRequest:request error:error];

if (![self save:error])
    return NO;

for (NSManagedObject *object in allObjects)
    [self deleteObject:object];

return YES;
}

然后使用这个简单地做：

- (void)deleteAllObjectsForEntityName:(NSString *) entity {

   NSError *error = nil;
   NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
   if (managedObjectContext != nil) {
       if (![managedObjectContext deleteAllObjectsForEntityName:entity withError:&error]) {
           NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
    }
 }
}

输入您的实体名称，它将全部删除:-)

于 2013-09-05T13:29:50.457 回答