Pushing a UIViewController from a modal view controller - iphone

Question

I am using a split view controller in an iPad app I am trying to make.
Right now, I have a view being displayed in a modal view controller using:
[self presentModalViewController:viewController animated:YES];
and that works fine, but when the user presses a button, I want the root view controller to push to another view. I am using:
RootViewController *rvc = [[RootViewController alloc] initWithNibName:#"RootViewController" bundle:nil];
[rcv pushViewController:rvc animated:YES];
but that is not working. What should I do?
--EDIT
Now, I am using
PhotosViewController *pv = [[PhotosViewController alloc] initWithNibName:#"PhotosViewController" bundle:nil];
[self.parentViewController.navigationController pushViewController:pv animated:YES];
NSLog(#"Navigation Controller: %#", self.parentViewController.naviagtionController);
When I do the NSLog call, it returns nil. Why is that?
Once again, I am using a split view controller and am trying to push the RootViewController to a new view.
Thanks

Answer 1

Your code isn't working because you're created a RootViewController instance and then trying to push it onto itself. What you should be doing is pushing the new view controller onto the parent view controller's navigation controller:
[self.parentViewController.navigationController pushViewController:newViewController animated:YES];

Answer 2

I know this is an old question but I believe the proper way "now" to push a viewController onto the main navigation stack from a modal viewController is to create a "didTapShowBlahViewController" delegate on the modal (this is assuming you want the user to be finished with the existing modal view and then push a new view onto the stack). Once you have that delegate, you simply have the view that initially invoked the modal to perform dismissing the modal and pushing the next view controller when the delegate is triggered.
- (void)didTapShowBlahViewController{
[self dismissViewControllerAnimated:YES completion: nil];
[self performSegueWithIdentifier:#"segueToBlahViewController" sender:self];
}
This is based on Apple's View Controller Programming Guide that specifies passing data to child view controllers and using delegates to pass data back to parents.
FYI: This way also ensures that the "back" button will not go back to the modal but instead to the view that invoked the modal, which is how modals are typically used.