Having Trouble Reading From Core Data - ios

Question

I have an array that the user can add objects to. I have a table view that lists "bad" ingredients the user does not want in their food. They can add these objects in an array, but I don't think Im reading them properly. I know for sure I'm writing properly because I make sure that my code checks for it.
This is how I add objects in Core Data:
-(void)addRow
{
UIAlertView *myAlertView = [[UIAlertView alloc] initWithTitle:#"Add a Bad Ingredient" message:#"Type the name of the ingredient" delegate:self cancelButtonTitle:#"Ok" otherButtonTitles:#"Cancel", nil];
myAlertView.alertViewStyle = UIAlertViewStylePlainTextInput;
[myAlertView show];
}
- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex{
NSManagedObjectContext *context = [self managedObjectContext];
AllergicIngredient *allergic = [NSEntityDescription insertNewObjectForEntityForName:#"AllergicIngredient" inManagedObjectContext:context];
NSString *enteredString = [[alertView textFieldAtIndex:0] text];
[allergic setValue:enteredString forKey:#"name"];
NSError *error;
if (![context save:&error])
{
NSLog(#"Couldnt find the save %#", error.localizedDescription);
}
else
{
NSLog(#"It saved properly");
}
[badIngredientsArray addObject:enteredString];
NSLog(#"%#", badIngredientsArray);
[self.tableView reloadData];
}
This is how I read from it (Making sure my array is getting Objects from core Data):
-(void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
NSManagedObjectContext *managedObjectContext = [self managedObjectContext];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:#"AllergicIngredient"];
badIngredientsArray = [[managedObjectContext executeFetchRequest:fetchRequest error:nil] mutableCopy];
[self.tableView reloadData];
}
I'm struggling with finding the errors in how I get read from it. So far, I'm not given any error messages or SIGABRTS, because the app just crashed when I try to go to the specific page where I'm fetching the data.

Answer 1

I see you're using a UITableView with Core Data.
Given the context, why don't you use an NSFetchResultsController?
If you use that, you will then be able to perform the following:
#pragma mark - Fetched Results Controller Section
- (NSFetchedResultsController *)fetchedResultsController {
if (_fetchedResultsController) {
return _fetchedResultsController;
}
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:[MyMO description]
inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];
// Specify how the fetched objects should be sorted
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#""
ascending:YES
selector:#selector(localizedStandardCompare:)];
[fetchRequest setSortDescriptors:[NSArray arrayWithObjects:sortDescriptor, nil]];
[fetchRequest setFetchBatchSize:20];
NSError *error = nil;
NSArray *fetchedObjects = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error];
if (fetchedObjects == nil) {
NSLog(#"Error Fetching: %#", error);
}
_fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest
managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:#"masterCache"];
_fetchedResultsController.delegate = self;
return _fetchedResultsController;
}
- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
[self.tableView beginUpdates];
}
- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
[self.tableView endUpdates];
}
- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath {
UITableView *tableView = self.tableView;
switch (type) {
case NSFetchedResultsChangeInsert:
[tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete:
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeUpdate: {
Person *changedPerson = [self.fetchedResultsController objectAtIndexPath:indexPath];
UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];
cell.textLabel.text = changedPerson.birthName;
}
break;
case NSFetchedResultsChangeMove:
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
[tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
default:
break;
}
}
- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id<NSFetchedResultsSectionInfo>)sectionInfo atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type {
switch (type) {
case NSFetchedResultsChangeInsert:
[self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete:
[self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
break;
default:
break;
}
}
And UITableView methods:
- (void)viewDidLoad
{
[super viewDidLoad];
NSError *error = nil;
if (![self.fetchedResultsController performFetch:&error]) {
NSLog(#"Error while fetching: %#", error);
abort();
}
}
#pragma mark - Table view data source
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
// Return the number of sections.
return [self.fetchedResultsController.sections count];
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
// Return the number of rows in the section.
id <NSFetchedResultsSectionInfo> sectionInfo = self.fetchedResultsController.sections[section];
return [sectionInfo numberOfObjects];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
CustomCell *cell = [tableView dequeueReusableCellWithIdentifier:#"Cell" forIndexPath:indexPath];
MyMo *mo = [self.fetchedResultsController objectAtIndexPath:indexPath];
// Configure the cell...
return cell;
}
- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {
return [self.fetchedResultsController.sections[section]name];
}
// Override to support editing the table view.
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
if (editingStyle == UITableViewCellEditingStyleDelete) {
NSManagedObjectContext *context = self.managedObjectContext;
MyMo *mo = [self.fetchedResultsController objectAtIndexPath:indexPath];
[context deleteObject:mo];
NSError *error = nil;
if (![context save:&error]) {
NSLog(#"Error saving: %#", error);
}
}
}