How do you pass data between views using a UINavigationController

CategoryViewController *viewController = [[CategoryViewController alloc] initWithNibName:@"CategoryViewController" bundle:[NSBundle mainBundle]];
self.categoryViewController.rootCategory = @"433";
self.categoryViewController = viewController;
[viewController release];

@property (nonatomic, readwrite) NSString *rootCategory;

CategoryViewController *viewController = [[CategoryViewController alloc] initWithNibName:@"CategoryViewController" bundle:[NSBundle mainBundle]];
viewController.rootCategory = @"433";
self.categoryViewController = viewController;
[viewController release];