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POCore Data One to Many Simple Example
 

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    <p>Been trying to create a One to Many relationship with core data with little progress.</p> <p>Just trying to make a simple core data example.</p> <p>Entity A = Type: typeName = String.</p> <p>Entity B = Routine: routineName = String.</p> <p>Relationship: Type has many routines.</p> <p>Ive got a few view controllers.</p> <ol> <li><p>TypeViewController (Table view controller to list all the Types from Entity A. </p></li> <li><p>AddTypeViewController (View controller to add a type to the entity through a typeTextField. This is pushed from a add button in the TypeViewController)</p></li> <li><p>RoutineViewController (Table view controller which is pushed when a type is selected from TypeViewController. Lists the routines from Entity B associated with the type selected.</p></li> <li><p>AddRoutineViewController (View controller to add Routine to entity B through routineNameTextField. This is pushed from a add button in the RoutineView Controller.</p></li> </ol> <p>I started off with implementing just the first Entity and managed to get the First 2 view controllers working. (Was able to add types and view them on the first view controller.</p> <p>Once i created the second entity and linked the relationship (also the inverse relationship too) the first part stopped working.</p> <p>Q. Do i have to change the way data is fetched in view controller 1? (As in this view controller i am only fetching data from Entity A).</p> <p>Q. Is it possible to be adding data separately? (adding type data from the view controller 2. and adding routine data from view controller 4.)</p> <p>Q. When saving data in view controller 4...</p> <pre><code>- (IBAction)savePressed:(id)sender { RoutinePlan *routinePlan = [[RoutinePlan alloc] initWithEntity:[NSEntityDescription entityForName:@"RoutinePlan" inManagedObjectContext:self.managedObjectContext] insertIntoManagedObjectContext:self.managedObjectContext]; [routinePlan setValue:self.rNameTextField.text forKey:@"rName"]; **How to add this routine to the selected type** NSError *savingError; if (![self.managedObjectContext save:&amp;savingError])NSLog(@"Error saving: %@", savingError); } </code></pre> <p>Thank you for any help. If any more information is needed i can provide it...</p> <p>Also does anyone know of a basic example out there of one to many relationships?</p> <p>EDIT:</p> <p>***Code snippet from TypeViewController.m</p> <pre><code>- (NSManagedObjectContext *)managedObjectContext{ NSManagedObjectContext *context = nil; id delegate = [[UIApplication sharedApplication] delegate]; if ([delegate performSelector:@selector(managedObjectContext)]) { context = [delegate managedObjectContext]; } return context;} - (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{ if ([[segue identifier] isEqualToString:@"current Type Selected"]) { NSManagedObject *selectedRoutine = [self.routineTypeArray objectAtIndex:[[self.tableView indexPathForSelectedRow] row]]; RoutinePlanViewController *destViewController = segue.destinationViewController; destViewController.routineTypeObject = selectedRoutine; }} - (void)viewDidAppear:(BOOL)animated{ [super viewDidAppear:animated]; // Fetch the devices from persistent data store NSManagedObjectContext *managedObjectContext = [self managedObjectContext]; NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:@"Type"]; self.routineTypeArray = [[managedObjectContext executeFetchRequest:fetchRequest error:nil] mutableCopy]; [self.tableView reloadData];} </code></pre> <p>**Code Snippet from AddTypeViewController.m</p> <pre><code>- (NSManagedObjectContext *)managedObjectContext { NSManagedObjectContext *context = nil; id delegate = [[UIApplication sharedApplication] delegate]; if ([delegate performSelector:@selector(managedObjectContext)]) { context = [delegate managedObjectContext]; } return context;} - (IBAction)savePressed:(id)sender { NSManagedObjectContext *context = [self managedObjectContext]; NSManagedObject *newRoutine = [NSEntityDescription insertNewObjectForEntityForName:@"Type" inManagedObjectContext:context]; [newRoutine setValue:self.rTypeTextField.text forKey:@"rType"]; NSError *error = nil; if (![context save:&amp;error]) { NSLog(@"Can't Save! %@ %@", error, [error localizedDescription]); } [self dismissViewControllerAnimated:YES completion:nil]; } </code></pre> <p>**Code Snippet from RoutineViewController.m</p> <pre><code>@synthesize routineTypeObject; - (NSManagedObjectContext *)managedObjectContext{ NSManagedObjectContext *context = nil; id delegate = [[UIApplication sharedApplication] delegate]; if ([delegate performSelector:@selector(managedObjectContext)]) { context = [delegate managedObjectContext]; } return context; } - (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender { if ([[segue identifier] isEqualToString:@"current Type Selected"]) { AddRoutineViewController *destViewController = segue.destinationViewController; destViewController.routineTypeObject = routineTypeObject; } } - (void)viewDidAppear:(BOOL)animated { [super viewDidAppear:animated]; // Fetch the devices from persistent data store NSManagedObjectContext *managedObjectContext = [self managedObjectContext]; NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:@"Routine"]; self.routineArray = [[managedObjectContext executeFetchRequest:fetchRequest error:nil] mutableCopy]; [self.tableView reloadData]; } </code></pre> <p>**Code Snippet from AddRoutineViewController.m</p> <pre><code>@synthesize routineTypeObject; - (NSManagedObjectContext *)managedObjectContext { NSManagedObjectContext *context = nil; id delegate = [[UIApplication sharedApplication] delegate]; if ([delegate performSelector:@selector(managedObjectContext)]) { context = [delegate managedObjectContext]; } return context; } - (IBAction)savePressed:(id)sender { Routine *routinePlan = [[Routine alloc] initWithEntity:[NSEntityDescription entityForName:@"Routine" inManagedObjectContext:self.managedObjectContext] insertIntoManagedObjectContext:self.managedObjectContext]; [routinePlan setValue:self.rNameTextField.text forKey:@"rName"]; **Error [Routine.Type = routineTypeObject]; NSError *savingError; if (![self.managedObjectContext save:&amp;savingError])NSLog(@"Error saving: %@", savingError); } </code></pre>
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Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

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