Using a FetchedResultsController to Auto-Populate a Table view below a TextField with entries from Core Data

Question 1

I guess self.autocompleteUrls is the NSMutableArray u had previously... Ok, U have come a long way, now see the autocompleteFetchedResultsController -> that is what fetches, and the condition if (_autocompleteFetchedResultsController != nil) protects property method from being called every time U reference autocompleteFetchedResultsController. So U should do something like this:

- (void)searchAutocompleteEntriesWithSubstring:(NSString *)substring {
    _autocompleteFetchedResultsController = nil;
    [self autocompleteFetchedResultsController];
    [self.testTableView reloadData];
}

and If U done everything else correctly that should be it...

Your cellFoRowAtIndexPath should look like this:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"autocomplete cell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];

    if(cell == nil){
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewStylePlain reuseIdentifier:CellIdentifier];
    }

    People *people = [self.autocompleteFetchedResultsController objectAtIndexPath:indexPath];
    cell.textLabel.text = people.name;
    return cell;
}

Question 2

Using the basic code from the Xcode library of snippets you can perform a Core Data fetch:

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"<#Entity name#>" inManagedObjectContext:<#context#>];
[fetchRequest setEntity:entity];

// Specifiy a predicate here if there are certain conditions your fetch must adhere to
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"<#Predicate string#>", <#Predicate arguments#>];
[fetchRequest setPredicate:predicate];

NSError *error = nil;
NSArray *fetchedObjects = [<#context#> executeFetchRequest:fetchRequest error:&error];
if (fetchedObjects == nil) {
    // Handle error
}

Replace the Entity name with the one that stores your NameTextField entries. And fetchedObjects is an array that will store your information you need to populate your table with.

Obviously, you will also need to save any new NameTextField entries to core data by creating a new entity and saving the context.

Question 3

I have sort of got this working. Rather than update the entire question, I have left that there for reference because I am sure someone will come across a similar situation. Through the use of a FetchedResultsController object within my view controller, I'm now getting a list of names to populate the table view that sits below the text field.

Let's look at some code:

- (NSFetchedResultsController *)autocompleteFetchedResultsController
{
    NSManagedObjectContext *managedObjectContext = [self managedObjectContext];
    if (_autocompleteFetchedResultsController != nil)
    {
        return _autocompleteFetchedResultsController;
    }
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];

    NSEntityDescription *entity = [NSEntityDescription entityForName:@"People" inManagedObjectContext:managedObjectContext];
    fetchRequest.entity = entity;

    if ([self.substring length] > 0) {
        NSPredicate *peoplePredicate = [NSPredicate predicateWithFormat:@"ANY name CONTAINS[c] %@", self.nameTextField.text];

        [fetchRequest setPredicate:personPredicate];
    }

    NSSortDescriptor *sort = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:NO];
    fetchRequest.sortDescriptors = [NSArray arrayWithObject:sort];
    NSFetchedResultsController *theFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:managedObjectContext sectionNameKeyPath:nil cacheName:nil];
    self.autocompleteFetchedResultsController = theFetchedResultsController;    _autocompleteFetchedResultsController.delegate = self;
    return _autocompleteFetchedResultsController;
}

- (void)viewDidLoad
{

    NSError *error;
    // I am performing the fetchHere and if there is an error, it will get logged.
    if (![[self autocompleteFetchedResultsController] performFetch:&error])
    {
        NSLog(@"Unresolved error %@ %@", error, [error userInfo]);
        exit(-1);
    }

    // Further code relating to tableview to make it hidden, etc
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    id  sectionInfo = [[_autocompleteFetchedResultsController sections] objectAtIndex:section];
    return [sectionInfo numberOfObjects];
}

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    self.testTableView.hidden = NO;
    self.substring = self.nameTextField.text];
    self.substring = [self.substring stringByReplacingCharactersInRange:range withString:self.substring];
    [self searchAutocompleteEntriesWithSubstring:self.substring];
    return YES;
}

#pragma mark UITableViewDataSource methods


- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"autocomplete cell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
    People *people = [self.autocompleteFetchedResultsController objectAtIndexPath:indexPath];
    cell.textLabel.text = people.name;
    return cell;
}

#pragma mark UITableViewDelegate methods

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {

    UITableViewCell *selectedCell = [tableView cellForRowAtIndexPath:indexPath];
    self.nameTextField.text = selectedCell.textLabel.text;

}

So this works to some extent. When I place the cursor in the nameTextField, it unhides the table view, but it currently shows me the name of ALL the names already entered.

What I want is the ability to, as I'm typing, for the table to only show me what matches that.

The [self searchAutocompleteEntriesWithSubstring:substring]; in the shouldChangeCharactersInRangeMethod is calling a custom method I created.

When I had this set to a NSMutableArray instead of using Core Data, it was the code below, but I have no idea how to adjust this code to say, search core data and only display the results that match what I am already typing.

- (void)searchAutocompleteEntriesWithSubstring:(NSString *)substring {

        self.autocompleteFetchedResultsController = nil;
        [self autocompleteFetchedResultsController];
        [self.testTableView reloadData];
}

I'm almost there - just need a bit of a push to get there!