ios - Making a relationship ordered causes "Dangling reference to an invalid object.” error while using context confinement

Question

After trying out AFIncrementalStore I've decided to do most of the work manually to have more control over what happens and when.

Object structure I have looks like this. "products" relationship is an ordered one.

Here's the code that runs inside a NSOperation

NSManagedObjectContext* childContext = [[NSManagedObjectContext alloc] initWithConcurrencyType: NSPrivateQueueConcurrencyType];
childContext.parentContext = self.parentManagedObjectContext;
[childContext performBlockAndWait: ^
{
    DashboardViewModel* dashboardViewModel = [NSEntityDescription insertNewObjectForEntityForName: @"DashboardViewModel"
                                                                           inManagedObjectContext: childContext];
    NSMutableOrderedSet* products = [NSMutableOrderedSet orderedSetWithCapacity: productRepresentations.count];
    for (NSDictionary* rawProductRepresentation in productRepresentations)
    {
        Product* product = [NSEntityDescription insertNewObjectForEntityForName: @"Product"
                                                         inManagedObjectContext: childContext];
        product.dashboardViewModel = dashboardViewModel;
        [products addObject: product];
    }

    dashboardViewModel.products = products;


    NSError* saveError = nil;
    if (![childContext save: &saveError])
        NSLog(@"Error: %@", saveError);

    //Save parent context to push changes to persistent store
    [self.parentManagedObjectContext performBlock: ^
    {
        NSError* saveParentError = nil;
        if (![childContext.parentContext save: &saveParentError])
            NSLog(@"Error: %@", saveParentError);
    }];
}];

Seems correct to me but I always get an error when saving parent context that says "Dangling reference to an invalid object.”</p>

Any suggestions?

Answer 1

你不应该设置关系的双方。核心数据为您设置了关系的反半部分，因此您可以删除您的productsset 并仅依赖 setting product.dashboardViewModel = dashboardViewModel。