We will start off by creating a new project and selecting a Window-based Application.

And naming it HelloWorld

Next we want to create a view controller. Go to File > New > New File… and select UIViewController subclass.

A UIViewController subclass works by overriding functions in its base class. The function of particular interest to us is the loadView. This is where we will add controls to our view.

[code lang=cpp]- (void)viewDidLoad
{
//Create a frame
CGRect frame = CGRectMake(0, 0, 320, 480);

//Initialize the view with our frame
self.view = [[UIView alloc] initWithFrame:frame];

//Set the background color of the view to be white
self.view.backgroundColor = [UIColor whiteColor];

[super viewDidLoad];
}[/code]

But before we add controles to the view, we need to create a frame which will hold the view. CGRect frame = CGRectMake(0, 0, 320, 480); creates a frame starting at point (0, 0) (the upper left corner) with a width of 320 pixels by 480 pixels (the size of an iPhone screen). We then allocate and initialize the view with the frame we just created. Now that we have a view, we can add our label.

[code lang=cpp]- (void)viewDidLoad
{
CGRect frame = CGRectMake(0, 0, 320, 480);
self.view = [[UIView alloc] initWithFrame:frame];
self.view.backgroundColor = [UIColor whiteColor];

//Create a frame to hold the label
frame = CGRectMake(50, 50, 100, 50);

//Create and initialize the label
UILabel *label = [[UILabel alloc] initWithFrame:frame];

//Set the labels text to Hello, World!
label.text = @"Hello, World!";

//Add the label to the view
[self.view addSubview:label];

//Release the reference
[label release];

[super viewDidLoad];
}[/code]

Like before, we start by creating a frame to hold the label. Once the frame is created, we can allocate a UILabel, initialize it, set its text, and add it to the view. Lastly, since Objective-C uses reference counting, it is a good idea to release the label to avoid any memory leaks – as a general rule of thumb, if you use a * make sure you release it.

Now that we have a view controller with a label, we need to add the view controller to the window. In your HelloWorldAppDelegate.h start by forward declaring the HelloWorldViewController class – this will tell the app delegate the HelloWorldViewController class exists. Then create an instance variable of type HelloWorldViewController, and finally make it a property.

[code lang=cpp]#import
//Forward declare the class
@class HelloWorldViewController;

@interface HelloWorldAppDelegate : NSObject {
//Create an instance variable (don't forget to release this)
HelloWorldViewController *viewController;
}

@property (nonatomic, retain) IBOutlet UIWindow *window;

//Create a property
@property (nonatomic, retain) HelloWorldViewController *viewController;

@end[/code]

Finally, in HelloWorldAppDelegate.m import the HelloWorldViewController.h file.
[code lang=cpp]#import "HelloWorldAppDelegate.h"

#import "HelloWorldViewController.h"[/code]

Synthesize the viewController instance variable

[code lang=cpp]@synthesize window=_window;
@synthesize viewController;[/code]

Then finally, allocate a HelloWorldViewController and add to the window viewController.view as a subview.

[code lang=cpp]- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
self.viewController = [HelloWorldViewController alloc];
[self.window addSubview:self.viewController.view];

// Override point for customization after application launch.
[self.window makeKeyAndVisible];
return YES;
}[/code]

Be sure to release viewController when you are done with it!

[code lang=cpp]- (void)dealloc
{
[viewController release];
[_window release];
[super dealloc];
}[/code]

Build and Go!