iphone - 通过iOS无法保存核心数据对象

Question

到目前为止，我已经成功保存了核心数据对象。在这段代码中，我正在搜索一些对象，并想要更新或向已保存的对象添加属性。

显然它不会保存更改，知道为什么吗？

NSManagedObjectContext *managedObjectContext = ((VentoAppDelegate*) [[UIApplication sharedApplication] delegate]).managedObjectContext;
NSEntityDescription *entityDescription = [NSEntityDescription entityForName:EntityNameString inManagedObjectContext:managedObjectContext];
NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease];
[request setEntity:entityDescription];

NSError *error;
NSArray *objects = [managedObjectContext executeFetchRequest:request error:&error];
if (objects == nil) {
    NSLog(@"Error - Events=nil - %@", [error localizedDescription]);
}
if ([objects count] > 0) {
    for (NSManagedObject* object in objects)    {
        if (distance <= maxDistance) {
            if (bla-bla-bla) {
                [object setValue:[NSNumber numberWithBool:YES] forKey:@"notification"];
                [self saveContext];
            }
        }
    }
}

谢谢!

Answer 1

如果更改托管对象，则仅在内存中进行更改。更改任何内容后，您需要保存托管上下文。添加如下内容:

NSError *error;
   if (![object.managedObjectContext save:&error]) {
   // Update to handle the error appropriately.
   NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
   abort();  // Fail
}