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POiPhone how to use NSPredicate to filter Core Data by the parent entity?
 

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  1. POiPhone how to use NSPredicate to filter Core Data by the parent entity?
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    <p>My core data is defined as this: user has many events; event has a single user relationship;</p> <p>Both user and event are core data entities. The user entity is passed in through a storyboard segue. </p> <p>I'm trying to configure NSPredicate to populate the detail UITableView for that user with only events for that particular user. </p> <p>So far I have tried</p> <pre><code>//does not work NSPredicate* onlyThisUserPredicate = [NSPredicate predicateWithFormat:@"user == %@",self.appUser]; //does not work NSPredicate* onlyThisUserPredicate = [NSPredicate predicateWithFormat:@"SELF.user == %@",self.appUser]; </code></pre> <p><strong>What is the proper syntax to compare events and only return those that have user object equal to the specified user object?</strong></p> <p>UPDATE:</p> <p>I'm trying to be able to add events to the user with this kind of fetched results controller:</p> <pre><code>-(NSFetchedResultsController*)fetchedResultsController { if (__fetchedResultsController != nil) { return __fetchedResultsController; } // Set up the fetched results controller. // Create the fetch request for the entity. NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; // Edit the entity name as appropriate. NSEntityDescription *entity = [NSEntityDescription entityForName:@"Event" inManagedObjectContext:[Event managedObjectContext]]; [fetchRequest setEntity:entity]; // Set the batch size to a suitable number. [fetchRequest setFetchBatchSize:20]; //I need to configure this user NSPredicate* onlyThisUserPredicate = [NSPredicate predicateWithFormat:@"user = %@",self.appUser]; // The first sort key must match the section name key path key if present, otherwise the initial dataset would be messed up: rows in incorrect sections NSString* firstSortKey = @"createDate"; NSSortDescriptor *firstSortDescriptor = [[NSSortDescriptor alloc] initWithKey:firstSortKey ascending:YES]; NSArray *sortDescriptors = [NSArray arrayWithObjects:firstSortDescriptor, nil]; [fetchRequest setSortDescriptors:sortDescriptors]; [fetchRequest setPredicate:onlyThisUserPredicate]; // Edit the section name key path and cache name if appropriate. // nil for section name key path means "no sections". NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:[Event managedObjectContext] sectionNameKeyPath:nil cacheName:@"Events"]; self.fetchedResultsController = aFetchedResultsController; aFetchedResultsController.delegate = self; // [aFetchedResultsController release]; [sortDescriptors release]; [fetchRequest release]; NSError *error = nil; if (![__fetchedResultsController performFetch:&amp;error]) { /* Replace this implementation with code to handle the error appropriately. abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. */ NSLog(@"Unresolved error %@, %@", error, [error userInfo]); // abort(); } return __fetchedResultsController; } </code></pre> <p>Thank you!</p>
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    1. PO
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    1. USAlex Stone
    1. USAlex Stone
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    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
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    2. PO
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    3. PO
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    1. This table or related slice is empty.
    1. COWhat results are you getting? Anything? Could you share the complete definition of your fetch request?
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      1. POiPhone how to use NSPredicate to filter Core Data by the parent entity?
      1. USvaldarin
    2. COFor some reason I'm getting 3 results for any user. If I manually check the number of events for a user using user.events.count, I get between 1 and 4. This tells me that my predicate is returning something but it is not correct.
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      1. POiPhone how to use NSPredicate to filter Core Data by the parent entity?
      1. USAlex Stone
 

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