Understanding Outlets in Interface Builder

Question

I'm doing an exercise to try to truly understand Interface Builder and Outlets.

Using Xcode 4.0 I've chosen the template for Window Based Application. I then:

1. Go into Interface Builder and add a UINavigation Controller.

2. Set the Window Outlet RootView Controller to the Navigation Controller.

3. Go to AppDelegate.h to create a UINavigation Controller called navController and give it an IBOutlet.

4. Go to AppDelegate.m in the didFinishLaunchingWithOptions to set self.window.rootViewController to self.navController.

5. Create a new UIViewController called FirstViewController complete with .xib file.

My question is, how do I set the root view controller in the mainWindow.xib outlet as the FirstViewController? But more importantly could someone explain to me the reasoning behind how you do this?

In other words, I would like FirstViewController to be the first view controller the user sees in my app. And I would like to understand exactly the mechanics behind making this happen.

Thanks for all the help!

Answer 1

interface bilder's outlets is just a links between graphical part of your program, and your code. In other words, they explane what code controlls this graphical object. You see, objective-c is very MVC-oriented. .xib file is V(view), outlet and your code, that linked with .xib by this outlet - is C(controller). M(model) should be somewhere alse in your code.

Now, about root view controller. I prefer implement it like below: import your firstViewController to AppDeledate.h and implement navigationController:

#import "firstViewController .h"
@class firstViewController
...
UINavigationController *navigationController;
...
@property (nonatomic, retain) IBOutlet UINavigationController *navigationController;

now, in interfacebuilder (mainWindow.xib), add navigationController object and link it with implemented property. Then, add a ViewController object in that navigationController, select this ViewController Object and set in inspectors it's class to firstViewController and xib file to firstViewController. Finaly, in AppDelegate.m in the didFinishLaunchingWithOptions to set self.window.rootViewController to self.navigationController. That's it.