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POFiltering with NSPredicate in one-to-many relationships
 

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    <p>I tried a lot of the solutions in stackoverflow but I'm not able to find a valid one. I have a core data model with two entities: Client and Destination. Both are wrapped by <code>NSManagedObject</code>subclasses.</p> <p>Client has some properties and a one-to-many relationship called destinations. Destination has a property called default_dest that is wrapped by a <code>NSNumber</code> and an inverse relationship called client.</p> <p>I have a <code>UITableViewController</code> where I'm using the following <code>fetchedController</code> property. The request works well. I'm able to retrieve clients stored in SQLite.</p> <pre class="lang-m prettyprint-override"><code>if (fetchedResultsController) return fetchedResultsController; NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"Client" inManagedObjectContext:self.managedObjectContext]; [fetchRequest setEntity:entity]; [fetchRequest setFetchBatchSize:20]; NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"code" ascending:YES]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; [fetchRequest setSortDescriptors:sortDescriptors]; fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:nil]; fetchedResultsController.delegate = self; [fetchRequest release]; [sortDescriptor release]; [sortDescriptors release]; return fetchedResultsController; </code></pre> <p>I would make another step. I would now filter the destinations retrieved from the previous request (that are contained in destinations <code>NSSet</code>) for each client. In particular, the destination can be added only if its default_dest value is 1.</p> <p>To fix this specification I tried to add an <code>NSPredicate</code> like the following:</p> <pre class="lang-m prettyprint-override"><code>NSPredicate* predicate = [NSpredicate predicateWithFormat:@"ANY destinations.default_dest == %@", [NSNumber numberWithInt:1]]; </code></pre> <p>Then I set it in fetchRequest as:</p> <pre class="lang-m prettyprint-override"><code>[fetchRequest setPredicate:predicate]; </code></pre> <p>Each time I run the request, it returns a "to-many-relationship fault destinations...". What does it mean?</p> <p>I've read <a href="https://stackoverflow.com/questions/3123950/iphone-core-data-relationship-fault">iphone-core-data-relationship-fault</a> but I don't understand what does it mean.</p> <p>So, my questions are: Is it possible to reach a similar goal? If yes, do you have any suggestions?</p> <p><strong>Notes</strong></p> <p>Obviously I could iterate over destinations set but I don't know if could be an expensive iteration and how many records there are.</p>
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