Question

I want to push root view controller. Why doesn’t this code work?

RootController *rootController = [[RootController alloc]initWithStyle:UITableViewStylePlain];               
[self.navigationController pushViewController:rootController animated:YES];
[rootController release];

I used addSubview like this before.

- (void)cancel {
    [self.navigationController popViewControllerAnimated:YES];
}

- (void)viewDidLoad { // this is root view controller
    [super viewDidLoad];

    UIBarButtonItem *cancelButton = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemCancel target:self action:@selector(cancel)];
    self.navigationItem.leftBarButtonItem = cancelButton;
    [cancelButton release];     
}

RootController *rootController = [[RootController alloc]initWithStyle:UITableViewStylePlain];               
UINavigationController *aNavigationController = [[UINavigationController alloc]initWithRootViewController:rootController];
self.naviController = aNavigationController;
[aNavigationController release];
[rootController release];
[self.view addSubview:[naviController view]];

And I added cancel button in navigation bar to go back to previous view. It doesn’t work.
So, I want to push instead of add.

Answer 1

You set the root controller in a UINavigationController using the

initWithRootViewController:

method. So, the way you are doing is correct. I would suggest you to inspect self.view and ensure that it is not nil.

EDIT: after your comment

You need to define a root view controller for your UINavigationController to work properly; from the UINavigationController reference:

Every navigation stack must have at least one view controller to act as the root.

So you cannot remove the root view controller. Possibly, to make things work as you like you should create an additional view controller to use as root view controller that you do not alter, then push your RootViewController on the navigation stack, then popping would work:

UIViewController *baseController = [[UIViewController alloc] initWithStyle:UITableViewStylePlain];               
UINavigationController *aNavigationController = [[UINavigationController alloc] initWithRootViewController:baseController];
self.naviController = aNavigationController;
[aNavigationController release];
[baseController release];
[self.view addSubview:[naviController view]];

RootController *rootController = [[RootController alloc] initWithStyle:UITableViewStylePlain];               
[self.navigationController pushViewController:rootController animated:YES];
[rootController release];

Notice that I first defined a simple UIViewController as root view controller, then pushed your controller on to it.

Once you do this, if you add the cancel button like you do, it will work popping the rootViewController from the navigation stack.

AFTER LAST COMMENT:

If I understand you right, when clicking on the cancel button, you want to get rid of the UINavigationController altogether.

In this case, use the following code for cancel:

- (void)cancel {
   [self.navigationController.view removeFromSuperview];
}

If this guess is right, keep in mind that since you are not keeping any reference to the navigation controller, it will be deallocated and with it all the view controllers you instantiated.

If instead of removing the UINavigationController altogether, you would simpy hide the navigation bar, then after popping rootController, call:

setNavigationBarHidden:animated