How to get Apples buggy "Locations" example to work?

Question

Unfortunately, Apple did not test it's tutorial at all. The "Locations" demo is really buggy and the edit Button does not even exist. I have no typo. First I didn't do copy & paste, and after that, I also attempted to just copy&paste their stuff. A lot of relevant code is completely missing.

They simply do this in view did load, without ever creating the edit button, anywhere:

- (void)viewDidLoad {

    [super viewDidLoad];

    // Set the title.
    self.title = @"Locations";

    // Configure the add and edit buttons.
    self.navigationItem.leftBarButtonItem = self.editButtonItem; // WTF?

    addButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(addEvent)];
    addButton.enabled = NO;
    self.navigationItem.rightBarButtonItem = addButton;

    // Start the location manager.
    [[self locationManager] startUpdatingLocation];

    /*
     Fetch existing events.
     Create a fetch request; find the Event entity and assign it to the request; add a sort descriptor; then execute the fetch.
     */
    NSFetchRequest *request = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Event" inManagedObjectContext:managedObjectContext];
    [request setEntity:entity];

    // Order the events by creation date, most recent first.
    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"creationDate" ascending:NO];
    NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
    [request setSortDescriptors:sortDescriptors];
    [sortDescriptor release];
    [sortDescriptors release];

    // Execute the fetch -- create a mutable copy of the result.
    NSError *error = nil;
    NSMutableArray *mutableFetchResults = [[managedObjectContext executeFetchRequest:request error:&error] mutableCopy];
    if (mutableFetchResults == nil) {
        // Handle the error.
    }

    // Set self's events array to the mutable array, then clean up.
    [self setEventsArray:mutableFetchResults];
    [mutableFetchResults release];
    [request release];
}

I went through the whole tutorial and it works so far, except that I can't delete cells because they didn't get that edit button right here.

I tried to fix that myself with this line in -viewDidLoad:

// Setup the buttons for the navigation bar
editButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemEdit target:self action:@selector(editEvent)];
self.navigationItem.leftBarButtonItem = editButton;

but now, what's the implementation of the editEvent method has to look like? Unfortunately all this stuff is completely missing in the Core Data tutorial.

Answer 1

Apple's code is fine. Although editButtonItem is an instance method rather than a read-only property, the dot syntax still works (since dot syntax is just shorthand for method calls--usually accessors).