Is a UINavigationController required to do pushViewController? - iphone

Question

I think the answer to my question is "Yes", but i just would like a confirmation from everyone.
I have a UITableView which should "slide" to another UIViewController when i select a row.
I've done this before with other apps (and they've included the UINavigationController, though in a UITabView).
So im wondering:
Is a UINavigationController required in order to use the self.navigationController pushViewController?
If so (which again i suspect to be true), where must I define the UINavigationController?
In the AppDelegate? In the main/primary UIViewController?

Answer 1

Yes, you will need to have a UINavigationController in order to do pushViewController. However, there is no one place where you must define it. If every view controller in your whole application is part of one UINavigationController, then it makes sense to put it in the App Delegate. You can, however, allocate and use a view controller at any time. (Notice that it is a UIViewController subclass.) You can also have multiple UINavigationControllers in your app (which is common, for example, if you have a Tab bar). So you can create UINavigationControllers at any time.
If you are looking for alternate ways of present other view controllers, you do have some different options. For example,
- (void)presentModalViewController:(UIViewController *)modalViewController animated:(BOOL)animated
will allow you to transition from one view controller to another view controller, and can be used without a UINavigationController. But I think the Navigation Controller is very often the best way to move from one view controller to another.

Answer 2

The short answer is: Yes.
UINavigationController was designed with the purpose of managing and animating a stack of view controllers on and off the screen (in conjunction with a few other interface elements such as a navigation bar, or a toolbar). Traditionally, UINavigationControllers are strongly held and initialized by the App Delegate, as they are considered a top-priority root object. An example class showing the proper usage of a UINavigationController might look like this:
#import <UIKit/UIKit.h>
#interface CFIExampleAppDelegate : NSResponder <UIApplicationDelegate>
#property (nonatomic, strong) UIWindow *window;
#property (nonatomic, strong) UINavigationController *navigationController;
#end
#implementation CFIExampleAppDelegate
-(BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
self.window = [[UIWindow alloc]initWithFrame:UIScreen.mainScreen.bounds];
self.navigationController = [[UINavigationController alloc]initWithRootViewController:/*Some Controller Instance*/];
self.window.rootViewController = self.navigationController;
[self.window makeKeyAndVisible];
return YES;
}
#end
The long answer, as always, is No.
UINavigationController can be trivially reimplemented (and it has, many times) to great effect. It's as simple as subclassing UIViewController and bolting on some kind of stack (like an NSMutableArray).