我在 Product 实体和 Cart 实体之间有一对多的关系。
用户需要有机会从购物车中删除产品。
我像这样获取产品：
// Fetch request for "Product":
NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"Product"];
// Fetch only products for the cart:
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"inCart = %@", self.cart];
[fetchRequest setPredicate:predicate];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"navn" ascending:YES];
[fetchRequest setSortDescriptors:@[sortDescriptor]];
self.fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:_theManagedObjectContext sectionNameKeyPath:nil cacheName:nil];
_fetchedResultsController.delegate = self;
并填充表格视图：
Product *prod = (Product *)[self.fetchedResultsController objectAtIndexPath:indexPath];
在表格视图中，我有一个按钮，当您点击它时，应该删除当前产品...我的“删除产品方法”中有以下代码
-(void)RemoveFromCart:(UIButton *)sender {
UITableViewCell *cell = (UITableViewCell *)sender.superview;
NSIndexPath *indexPath = [_Table indexPathForCell:cell];
Product *prod = (Product *)[self.fetchedResultsController objectAtIndexPath:indexPath];
/*_cart is retrieved when the user pushes the add to cart button, in another viewcontroller, a cart object is then returned and passed to the cart viewcontroller */
NSMutableSet *mutableSet = [NSMutableSet setWithSet:_cart.products];
[mutableSet removeObject:prod];
_cart.products = mutableSet;
[self saveCurrentContext:_theManagedObjectContext];
[_Table reloadData];
}
但是，当方法被触发时，什么也没有发生。产品没有从关系中删除。我该如何解决这个问题，我的代码在某处显然是错误的。