How to disable a DetailViewController UIBarButtonItem from RootViewController?

Question

i have a main table view. and a DetailView. when cell is clicked, DetailView of that cell comes which shows details of that cell. DetailView has two buttons next and previous. I wanna know how to disable a detail view button from RootViewcontroller.m. code looks like this:

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

    DetailViewController *nextController = [[DetailViewController alloc] init];
    int storyIndex = [indexPath indexAtPosition:[indexPath length] -1];
    nextController = [nextController initWithObjectAtIndex:storyIndex inArray:stories];

    NSString *storyTitle = [[stories objectAtIndex:storyIndex] objectForKey:@"title"];
    nextController.title = @"Details";

    UIBarButtonItem *tempButtonItem = [[[UIBarButtonItem alloc] init] autorelease];
    tempButtonItem.title = @"Back";

    self.navigationItem.backBarButtonItem = tempButtonItem ;

    nextController.sTitle = storyTitle;
    [self.navigationController pushViewController:nextController animated:YES];

    [nextController release];

}

i have already tried nextController.next.enabled=NO and [nextController.next setEnabled:NO] after this line: [self.navigationController pushViewController:nextController animated:YES];

where next is the UIBarButtonItem name which is in DetailViewController. can anybody tell me how to disable that button. thanx in advance

Answer 1

Viewcontrollers and views are not loaded at the same time. What this means is that when you instantiate an object of DetailViewController in your case, the views are not drawn(and if you are using Nib's) loaded, this is part of the lazy loading concept.

So the first time you send the message setEnabled = NO, the object will be nil(sending messages to objects that are nil is allowed in Objective C).

Example:

[nextController setEnabled:NO] is equal to [nil setEnabled:NO] and this is surely not what you want.

The next time, unless a memory warning and the views are unloaded, the views will be in memory and the reference to the button will no longer be nil so the second time you invoke it, it will work.

And add the code line above the pushViewController:animate

If you want to initialize the button to be disable you may put this code in the viewDidLoad/viewWillAppear depending on the context of your application.

This is only one possible solution.

---

Edited answer to request in comment:

In your initializer method in the DetailviewController add this:

self.navigationItem.leftBarButtonItem = [[[UIBarButtonItem alloc] initWithTitle:@"Back" style:UIBarButtonItemStyleBordered target:self action:@selector(backToRoot)] autorelease];

- (void)backToRoot {
    [self.navigationController popToRootViewControllerAnimated:YES];
}

and also add the method-signature to your headerfile.

Reference to the UINavigationController: http://developer.apple.com/library/ios/#documentation/uikit/reference/UINavigationController_Class/Reference/Reference.html