ios – 核心数据：删除/添加对象时出错

当我想通过下载和解析json文件来更新我的Core Data文件时,我的应用程序有时会崩溃.我收到以下错误：

如果我在迭代期间更改属性,在迭代中保存NsmanagedObjectContext的位置是否重要？

这是我的代码：

- (void) updateData
{           
    dispatch_queue_t serialdQueue;
    serialdQueue = dispatch_queue_create("update",null);
    dispatch_async(serialdQueue,^{
        [self method1];
    });
    dispatch_async(serialdQueue,^{
        [self method2];
    });
    dispatch_async(serialdQueue,^{
        [self method3];
    });
    dispatch_async(serialdQueue,^{
        [self method4];
    });
    dispatch_async(serialdQueue,^{
        [self method5];
    });

}

-(void)method1
{        
    //DOWNLOAD JSON FILE
}

-(void)method2 //here i add objects to the core data file
{        
    @try {

        for (NSDictionary *jsonActivity in [json objectForKey:@"Activities"]) {  //ITERATE THROUGH JSON ACTIVITY ARRAY

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

            NSEntityDescription *entity = [NSEntityDescription entityForName:@"Activity" inManagedObjectContext:self.managedObjectContext];
            [request setEntity:entity];

            NSPreDicate *searchFilter = [NSPreDicate preDicateWithFormat:@"title == %@",[jsonActivity objectForKey:@"title"]]; // checK IF OBjeCT FROM JSON FILE ALREADY EXISTs...
            [request setPreDicate:searchFilter];
            NSError *error = nil;

            NSArray *results = [self.managedObjectContext executeFetchrequest:request error:&error];
            if (error) {
                NSLog(@"Error %@",error);
                abort();
            }

            if ([results count] == 0) { // ADD NEW ACTIVITY IF OLD LIST DOESNT CONTAIN IT

                Activity *activity = [NSEntityDescription insertNewObjectForEntityForName:@"Activity" inManagedObjectContext:self.managedObjectContext];

                activity.title = [jsonActivity objectForKey:@"title"];

                activity.remove = [NSnumber numberWithBool:NO]; // REMOVE FLAG = NO BECAUSE NEW OBjeCTS AREN'T REMOVED

            } else  {

                Activity *activity = (Activity*) [results objectATindex:0];
                activity.remove = [NSnumber numberWithBool:NO]; // IF OBjeCT ALREADY EXISTS IT SHOULD BE OBTAINED
            }

            AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
            [appDelegate saveContext]; // SAVE MO COntexT
        }

    }   @catch (NSException *exception) {

        NSLog(@"Exception: %@",exception);
    }
}

-(void)method3 // deletE OLD OBjeCTS 
{   
    NSFetchrequest *fetchrequest = [[NSFetchrequest alloc] init];
    NSEntityDescription *entityDescription = [NSEntityDescription entityForName:@"Activity" inManagedObjectContext:self.managedObjectContext];
    [fetchrequest setEntity:entityDescription];

    NSPreDicate *searchFilter = [NSPreDicate preDicateWithFormat:@"remove == %@",[NSnumber numberWithBool:YES]];
    [fetchrequest setPreDicate:searchFilter];

    NSArray *objectsTodelete = [[NSArray alloc] init];

    NSError *error = nil;
    objectsTodelete = [self.managedObjectContext executeFetchrequest:fetchrequest error:&error];
    if (error) {
        NSLog(@"Error %@",error);
        abort();
    }

    for (Activity *activity in objectsToDelete) { // deletE OBjeCTS WITH THE PROPERTY REMOVE = YES

        [self.managedObjectContext deleteObject:activity]; // deletE ACTIVITY
    }

    AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
    [appDelegate saveContext]; // SAVE MO COntexT
}

-(void)method4 // CHANGE THE REMOVE PROPERTY TO YES OF ALL OBjeCTS
{        
    NSFetchrequest *fetchrequest = [[NSFetchrequest alloc] init];
    NSEntityDescription *entityDescription = [NSEntityDescription entityForName:@"Activity" inManagedObjectContext:self.managedObjectContext];
    [fetchrequest setEntity:entityDescription];

    NSArray *objects = [[NSArray alloc] init];

    NSError *error = nil;
    objects = [self.managedObjectContext executeFetchrequest:fetchrequest error:&error];
    if (error) {
        NSLog(@"Error %@",error);
        abort();
    }

    for (Activity *activity in objects) {

        activity.remove = [NSnumber numberWithBool:YES];
    }

    AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
    [appDelegate saveContext]; // SAVE MO COntexT

    NSLog(@"End update");
}

-(void)method5 //updatE UI
{
    //UI updatES
}

//asyncrhonous
[self.managedObjectContext performBlock:^{
    //do stuff with the context
}];

//syncrhonous
[self.managedObjectContext performBlockAndWait:^{
    //do stuff with the context
}];