Question

Removed the colon which wasn’t supposed to be there since my selector doesn’t have one. It fixed it, then this problem occurred:

    2012-06-02 22:33:10.083 TinyPix[10433:fb03] load OK
2012-06-02 22:33:10.084 TinyPix[10433:fb03] *** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<BIDTinyPixDocument 0x6e665a0> valueForUndefinedKey:]: this class is not key value coding-compliant for the key timeStamp.'
*** First throw call stack:
(0x16b0022 0x1841cd6 0x16afee1 0x9c8efe 0x937831 0x936c99 0x5f47 0x5e77 0x93af30 0x93aedb 0x59ed 0x4546e3 0x40778d9 0x4078509 0x15e7803 0x15e6d84 0x15e6c9b 0x15997d8 0x159988a 0x1b626 0x2a5d 0x29c5)
terminate called throwing an exception

Here’s my detail file: I’m getting a SIGABRT error on the self.detailDescriptionLabel.text line. Don’t know what’s going on.

#import "BIDDetailViewController.h"

@interface BIDDetailViewController ()
- (void)configureView;
@end

@implementation BIDDetailViewController

@synthesize detailItem = _detailItem;
@synthesize detailDescriptionLabel = _detailDescriptionLabel;

#pragma mark - Managing the detail item

- (void)setDetailItem:(id)newDetailItem
{
    if (_detailItem != newDetailItem) {
        _detailItem = newDetailItem;

        // Update the view.
        [self configureView];
    }
}

- (void)configureView
{
    // Update the user interface for the detail item.

    if (self.detailItem) {
        self.detailDescriptionLabel.text = [[self.detailItem valueForKey:@"timeStamp"] description];
    }
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    [self configureView];
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    self.detailDescriptionLabel = nil;
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}

@end

Here’s my file:

#import "BIDMasterViewController.h"
#import "BIDTinyPixDocument.h"

#import "BIDDetailViewController.h"

@interface BIDMasterViewController () <UIAlertViewDelegate>

@property (strong, nonatomic) NSArray *documentFilenames;
@property (strong, nonatomic) BIDTinyPixDocument *chosenDocument;
-(NSURL *)urlForFilename:(NSString *)filename;
-(void)reloadFiles;
- (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath;
@end

@implementation BIDMasterViewController
@synthesize colorControl;
@synthesize documentFilenames;
@synthesize chosenDocument;

@synthesize fetchedResultsController = __fetchedResultsController;
@synthesize managedObjectContext = __managedObjectContext;

- (void)awakeFromNib
{
    [super awakeFromNib];
}

-(void)viewWillAppear:(BOOL)animated;
{
    [super viewWillAppear:animated];
    NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
    NSInteger selectedColorIndex = [prefs integerForKey:@"selectedColorIndex"];
    self.colorControl.selectedSegmentIndex = selectedColorIndex;

}


- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    self.navigationItem.leftBarButtonItem = self.editButtonItem;

    UIBarButtonItem *addButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(insertNewObject:)];
    self.navigationItem.rightBarButtonItem = addButton;

    [self reloadFiles];
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}

- (void)insertNewObject
{
// get the name
    UIAlertView *alert =
    [[UIAlertView alloc] initWithTitle:@"Filename"
                               message:@"Enter a name for your new TinyPix document."
                              delegate:self
                     cancelButtonTitle:@"Cancel"
                     otherButtonTitles:@"Create", nil];
    alert.alertViewStyle = UIAlertViewStylePlainTextInput;
    [alert show];
}

#pragma mark - Table View



- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath
{
    // Return NO if you do not want the specified item to be editable.
    return YES;
}

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (editingStyle == UITableViewCellEditingStyleDelete) {
        NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
        [context deleteObject:[self.fetchedResultsController objectAtIndexPath:indexPath]];

        NSError *error = nil;
        if (![context save:&error]) {
             // Replace this implementation with code to handle the error appropriately.
             // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. 
            NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
            abort();
        }
    }   
}

- (BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath
{
    // The table view should not be re-orderable.
    return NO;
}



#pragma mark - Fetched results controller

- (NSFetchedResultsController *)fetchedResultsController
{
    if (__fetchedResultsController != nil) {
        return __fetchedResultsController;
    }

    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    // Edit the entity name as appropriate.
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Event" inManagedObjectContext:self.managedObjectContext];
    [fetchRequest setEntity:entity];

    // Set the batch size to a suitable number.
    [fetchRequest setFetchBatchSize:20];

    // Edit the sort key as appropriate.
    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"timeStamp" ascending:NO];
    NSArray *sortDescriptors = [NSArray arrayWithObjects:sortDescriptor, nil];

    [fetchRequest setSortDescriptors:sortDescriptors];

    // Edit the section name key path and cache name if appropriate.
    // nil for section name key path means "no sections".
    NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:@"Master"];
    aFetchedResultsController.delegate = self;
    self.fetchedResultsController = aFetchedResultsController;

    NSError *error = nil;
    if (![self.fetchedResultsController performFetch:&error]) {
         // Replace this implementation with code to handle the error appropriately.
         // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. 
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }

    return __fetchedResultsController;
}    

- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller
{
    [self.tableView beginUpdates];
}

- (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;
    }
}

- (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:
            [self configureCell:[tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];
            break;

        case NSFetchedResultsChangeMove:
            [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
            [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]withRowAnimation:UITableViewRowAnimationFade];
            break;
    }
}

- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller
{
    [self.tableView endUpdates];
}

/*
// Implementing the above methods to update the table view in response to individual changes may have performance implications if a large number of changes are made simultaneously. If this proves to be an issue, you can instead just implement controllerDidChangeContent: which notifies the delegate that all section and object changes have been processed. 

 - (void)controllerDidChangeContent:(NSFetchedResultsController *)controller
{
    // In the simplest, most efficient, case, reload the table view.
    [self.tableView reloadData];
}
 */

- (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath
{
    NSManagedObject *object = [self.fetchedResultsController objectAtIndexPath:indexPath];
    cell.textLabel.text = [[object valueForKey:@"timeStamp"] description];
}

-(NSURL *)urlForFilename:(NSString *)filename {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentDirectory = [paths objectAtIndex:0];
    NSString *filePath = [documentDirectory stringByAppendingPathComponent:filename];
    NSURL *url = [NSURL fileURLWithPath:filePath];
    return url;
}

-(void)reloadFiles {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *path = [paths objectAtIndex:0];
    NSFileManager *fm = [NSFileManager defaultManager];

    NSError *dirError;
    NSArray *files = [fm contentsOfDirectoryAtPath:path error:&dirError];
    if (!files) {
        NSLog(@"Encountered error while trying to list files in directory %@: %@", path, dirError);
    }

    NSLog(@"found files: %@", files);

    files = [files sortedArrayUsingComparator:^NSComparisonResult(id filename1, id filename2) {
        NSDictionary *attr1 = [fm attributesOfItemAtPath:[path stringByAppendingPathComponent:filename1]
                                                   error:nil];
        NSDictionary *attr2 = [fm attributesOfItemAtPath:[path stringByAppendingPathComponent:filename2]
                                                                                        error:nil];
                               return [[attr2 objectForKey:NSFileCreationDate] compare:[attr1 objectForKey:NSFileCreationDate]];
                               }];

        self.documentFilenames = files;
        [self.tableView reloadData];

}

-(NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    return 1;
}

-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return [self.documentFilenames count];
}

-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"FileCell"];

    NSString *path = [self.documentFilenames objectAtIndex:indexPath.row];
    cell.textLabel.text = path.lastPathComponent.stringByDeletingPathExtension;
    return cell;
}


-(IBAction)chooseColor:(id)sender {
    NSInteger selectedColorIndex = [(UISegmentedControl *)sender selectedSegmentIndex];
    NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
    [prefs setInteger:selectedColorIndex forKey:@"selectedColorIndex"];
}


-(void)alertView:(UIAlertView *)alertView
didDismissWithButtonIndex:(NSInteger)buttonIndex {
    if (buttonIndex == 1) {
        NSString *filename = [NSString stringWithFormat:@"%@.tinypix",
                              [alertView textFieldAtIndex:0].text];
        NSURL *saveUrl = [self urlForFilename:filename];
        self.chosenDocument = [[BIDTinyPixDocument alloc] initWithFileURL:saveUrl];
        [chosenDocument saveToURL:saveUrl
                 forSaveOperation:UIDocumentSaveForCreating
                completionHandler:^(BOOL success) {
                    if (success) {
                        NSLog(@"save OK");
                        [self reloadFiles];
                        [self performSegueWithIdentifier:@"masterToDetail"
                                                  sender:self];
                    } else {
                        NSLog(@"failed to save!");
                    }
                }];
    }
}


-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    if (sender == self) {
        // if sender == self, a new document has just been created,
        // and chosenDocument is already set.

        UIViewController *destination = segue.destinationViewController;
        if ([destination respondsToSelector:@selector(setDetailItem:)]) {
            [destination setValue:self.chosenDocument forKey:@"detailItem"];
        }
    }else {
        // find the chose document from the tableview
        NSIndexPath *indexPath = [self.tableView indexPathForSelectedRow];
        NSString *filename = [documentFilenames objectAtIndex:indexPath.row];
        NSURL *docUrl = [self urlForFilename:filename];
        self.chosenDocument = [[BIDTinyPixDocument alloc] initWithFileURL:docUrl];
        [self.chosenDocument openWithCompletionHandler:^(BOOL success) {
            if (success) {
                NSLog(@"load OK");
                UIViewController *destination = segue.destinationViewController;
                if ([destination respondsToSelector:@selector(setDetailItem:)]) {
                    [destination setValue:self.chosenDocument forKey:@"detailItem"];
                }
            }else {
                NSLog(@"failed to load!");
            }
        }];
    }
}
@end

Answer 1

You specify the selector as insertNewObject: and the colon on the end says that it takes one parameter. The insertNewObject method you implemented takes no parameters and, to Objective-C, that makes it a different thing and it can’t find the one parameter method.

You should change your implementation to - (IBAction)insertNewObject:(id)sender {...} to match @selector(insertNewObject:).