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POFetching child objects belongs to parent object & put them in tableView (core-data, relationships)
 

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  1. POFetching child objects belongs to parent object & put them in tableView (core-data, relationships)
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    <p>I have two tableViews, the main one adds the parent object, and when you click on a parent object in the tableView, it takes you to the child tableView, I did the first part successfully, but when it comes to fetching the "RIGHT" child objects I get confused, I way I do it is that I fetch ALL child object, the using enumeration I pick the right ones and put then into a NSSet, but that doesn't work, here's the child object table view.m: </p> <pre><code> #import "MinorGoalsTableViewController.h" @interface MinorGoalsTableViewController () @end @implementation MinorGoalsTableViewController @synthesize selectedGoal = _selectedGoal; @synthesize fetchedResultsController = _fetchedResultsController; @synthesize minorGoalsSet; // init with goal (for GTVC) - (id) initWithGoal:(Goal *)goal { if (self = [super init]) { _selectedGoal = goal; } return self; } - (id)initWithStyle:(UITableViewStyle)style { self = [super initWithStyle:style]; if (self) { // Custom initialization } return self; } - (void)viewDidLoad { [super viewDidLoad]; NSError *error = nil; // Uncomment the following line to preserve selection between presentations. // self.clearsSelectionOnViewWillAppear = NO; // Uncomment the following line to display an Edit button in the navigation bar for this view controller. // self.navigationItem.rightBarButtonItem = self.editButtonItem; NSLog(@"Minor Goals in %@ are: %lu", self.selectedGoal.title , (unsigned long)[self.selectedGoal.minorGoal count]); // self.minorGoalsSet = nil; // initializing minorGoalsSet self.minorGoalsSet = [[NSMutableSet alloc] init]; // performing fetch if (![self.fetchedResultsController performFetch:&amp;error]) { NSLog(@"Error fetching all minor goals: %@", error); abort(); } // creating NSSet that will carry all selectedGoal minor goals NSSet *minorGoals = self.selectedGoal.minorGoal; // creating a loop to add minor goals in minorGoalsSet // add existing minor goals in selected goal to minorGoalsSet for (MinorGoal *minor in minorGoals) { [minorGoalsSet addObject:minor]; } NSLog(@"minor goals in set: %lu", (unsigned long) [minorGoalsSet count]); NSLog(@"minor goals in set2: %lu", (unsigned long) [minorGoals count]); // setting nav title to selected goal title self.navigationItem.title = _selectedGoal.title; // adding "add" button to nav self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(addNewMinorGoal)]; } - (void) viewWillDisappear:(BOOL)animated { self.selectedGoal = nil; } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // Dispose of any resources that can be recreated. } </code></pre> <h1>pragma mark - Table view data source</h1> <pre><code> - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { return [self.selectedGoal.minorGoal count]; // id &lt;NSFetchedResultsSectionInfo&gt; secInfo = [[self.fetchedResultsController sections] objectAtIndex:section]; // return [secInfo numberOfObjects]; } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier]; } cell.accessoryType = UITableViewCellAccessoryNone; // Configure the cell... MinorGoal *minor = [self.fetchedResultsController objectAtIndexPath:indexPath]; // well see about that later if ([minorGoalsSet containsObject:minor]) { cell.textLabel.text = minor.title; } // setting cell's title to minor goal's title // cell.textLabel.text = minor.title; return cell; } </code></pre> <h1>pragma mark - fetched results controller method</h1> <pre><code> - (NSFetchedResultsController*) fetchedResultsController { if (_fetchedResultsController != nil) { return _fetchedResultsController; } // creating fetch request NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"MinorGoal" inManagedObjectContext:self.selectedGoal.managedObjectContext]; [fetchRequest setEntity:entity]; NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"title" ascending:NO]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; [fetchRequest setSortDescriptors:sortDescriptors]; // setting _fetchedResultsController _fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.selectedGoal.managedObjectContext sectionNameKeyPath:nil cacheName:nil]; // performing fetch NSError *error = nil; if (![self.fetchedResultsController performFetch:&amp;error]) { NSLog(@"Error fetching minors: %@", error); } // returning return _fetchedResultsController; } </code></pre> <h1>pragma mark - Table view delegate</h1> <pre><code> - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { } - (void) addNewMinorGoal { // code to show UIAlertView that will add new minor goal // creating UIAlertView UIAlertView *addMinorGoalAlert = [[UIAlertView alloc] initWithTitle:@"Add Minor Goal" message:@"Minor Goal Title" delegate:self cancelButtonTitle:@"Cancel" otherButtonTitles:@"Save", nil]; // Adding plain textfield for minor goal title addMinorGoalAlert.alertViewStyle = UIAlertViewStylePlainTextInput; // showing UIAlertView [addMinorGoalAlert show]; } </code></pre> <h1>pragma mark - UIAlertView for Add New Minor Delegation</h1> <pre><code> - (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex { if (buttonIndex == 0) { NSLog(@"Adding Minor Goal Canceled!"); } else { // creating string will carry textField value NSString *minorTitle = [[alertView textFieldAtIndex:0]text]; // creating new minor goal MinorGoal *newMinorGoal = [NSEntityDescription insertNewObjectForEntityForName:@"MinorGoal" inManagedObjectContext:self.selectedGoal.managedObjectContext]; // setting title of new minor goal newMinorGoal.title = minorTitle; [self.selectedGoal addMinorGoalObject:newMinorGoal]; // saving NSError *error = nil; if (![self.selectedGoal.managedObjectContext save:&amp;error]) { NSLog(@"Error saving new minor goal: %@", error); } NSLog(@"we save %@ to %@ and theres %lu in it", newMinorGoal.title, self.selectedGoal.title, (unsigned long) [self.selectedGoal.minorGoal count]); // fetching [self.fetchedResultsController performFetch:&amp;error]; // reloading tableView data [self.tableView reloadData]; } } @end </code></pre> <p>Just tell me the right way to fetch the right child object, and should i put them in a NSSet?</p>
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    1. COwhy don't you just do NSArray *normalChilds = [parent.childs.allObjects sortedArrayUsingSortDescriptors:@[[NSSOrtDescriptor sortDescriptorWithKey:@"title" ascending:YES]];
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    2. COparent.childs.allObjects returns NSSet. @iiFreeman
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