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POWhy is Core Data losing one of my values?
 

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  1. POWhy is Core Data losing one of my values?
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    <p>Inside my user object I have the following code to generate a new 'session' or continue the existing session if one exists.</p> <p>Strangely it will keep other properties but just loses the 'user' property... user is in a one to many relationship with session, 1 user can have many sessions. (or will do, for the following test I am simply checking for any previous session and using it if it exists)</p> <pre><code>-(void)setupSessionStuff { // Create new Core Data request NSFetchRequest *request = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"Session" inManagedObjectContext:[self managedObjectContext]]; [request setEntity:entity]; // Create Sort Descriptors for request NSSortDescriptor *startTimeSort = [[NSSortDescriptor alloc] initWithKey:@"startTime" ascending:NO selector:nil]; [request setSortDescriptors:[NSArray arrayWithObjects:startTimeSort, nil]]; [startTimeSort release]; [request setFetchLimit:1]; // Only get the most recent session // Execute request NSError *error = nil; NSArray *results = [[self managedObjectContext] executeFetchRequest:request error:&amp;error]; if (results == nil) { // Something went horribly wrong... NSLog(@"Unresolved error %@, %@", error, [error userInfo]); exit(-1); } [request release]; Session *theSession = nil; if ([results count] == 1) { NSLog(@"existing session"); // Use existing Session theSession = [results objectAtIndex:0]; NSLog(@"session.user: %@", [theSession valueForKey:@"user"]); // this is always null! } else { NSLog(@"new session"); // Create new Sesson theSession = (Session *)[NSEntityDescription insertNewObjectForEntityForName:@"Session" inManagedObjectContext:[self managedObjectContext]]; // Add the Session to the User NSLog(@"before: session.user: %@", theSession.user); // null theSession.user = self; NSLog(@"after: session.user: %@", theSession.user); // looks good } ... NSLog(@"before.save: session.user: %@", theSession.user); // good // Save everything error = nil; if (![[self managedObjectContext] save:&amp;error]) { // Something went horribly wrong... NSLog(@"Unresolved error: %@, %@, %@", error, [error userInfo],[error localizedDescription]); exit(-1); } NSLog(@"after.save: session.user: %@", theSession.user); // still there.. } </code></pre> <p>Additionally I have opened up the Core Data sqlite file and examined with SQLite Manager. It <em>looks</em> like the relationship has been correctly saved, as I can see the userID stored in the session table.</p> <p>-</p> <p>Just added this at the start of my method as another test.</p> <pre><code>NSSet *set = self.session; for(Session *sess in set) { NSLog(@"startTime %@", sess.startTime); NSLog(@"user %@", sess.user); } </code></pre> <p>Strangely enough the user is set in this case!? So set here then not set a few lines later when I do the fetch request... ?</p> <p>-</p> <p>In response to feedback below</p> <p>Have added this code after assigning <code>session.user = self</code> and both return the expected output. So it does look like the problem is with the subsequent fetch.</p> <pre><code>NSLog(@"self.session: %@", self.session); NSLog(@"self.session: %@", [self valueForKey:@"session"]); </code></pre> <p>Also I agree that accessing my session's through self.session will let me work around my issue, but it doesn't solve what is going on here. In other places I surely won't be able to walk from one entity to the other so need to confidence the fetch is going to pull everything in correctly.</p>
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    1. COHave you set up the inverse relationship for Session to user(s)? If you dont then the full set/relationship maintenance wont get done for you.
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      1. USWarren Burton
    2. COYes I have the inverse connection set up in the model.
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