Xcode - Objective C 2.0

#import <UIKit/UIKit.h>

@class MyViewController;

@interface HelloWorldAppDelegate : NSObject <UIApplicationDelegate> {

IBOutlet UIWindow *window;
MyViewController *myViewController;
}

@property (nonatomic, retain) UIWindow *window;
@property (nonatomic, retain) MyViewController *myViewController;

@end

#import "HelloWorldAppDelegate.h"
#import "MyViewController.h"


@implementation HelloWorldAppDelegate

@synthesize window;
@synthesize myViewController;


- (void)applicationDidFinishLaunching:(UIApplication *)application {

// Set up the view controller
MyViewController *aViewController = [[MyViewController alloc] initWithNibName:@"HelloWorld" bundle:[NSBundle mainBundle]];
self.myViewController = aViewController;
[aViewController release];

// Add the view controller's view as a subview of the window
UIView *controllersView = [myViewController view];
[window addSubview:controllersView];
[window makeKeyAndVisible];
}


- (void)dealloc {
[myViewController release];
[window release];
[super dealloc];
}

@end

#import <UIKit/UIKit.h>

@interface MyViewController : UIViewController <UITextFieldDelegate> {

IBOutlet UITextField *textField;
IBOutlet UILabel *label;
NSString *string;
}

@property (nonatomic, retain) UITextField *textField;
@property (nonatomic, retain) UILabel *label;
@property (nonatomic, copy) NSString *string;

- (IBAction)changeGreeting:(id)sender;

@end

#import "MyViewController.h"


@implementation MyViewController

@synthesize textField;
@synthesize label;
@synthesize string;


- (IBAction)changeGreeting:(id)sender {

// Set our model value -- it's not used anywhere else at the moment, but it illustrates the principle
self.string = textField.text;

NSString *nameString = string;

// If the user entered an empty string, set the name string to "World"
if ([nameString length] == 0) {
nameString = @"World";
}

// Create a new string for the label
NSString *greeting = [[NSString alloc ] initWithFormat:@"Hello, %@!", nameString];
label.text = greeting;
/*
The greeting string was created with 'alloc', so to adhere to memory managment conventions, now release it. It's the label's responsibility to take ownership of the greeting string when its text is set.
*/
[greeting release];
}


- (BOOL)textFieldShouldReturn:(UITextField *)theTextField {
// When the user presses return, take focus away from the text field so that the keyboard is dismissed.
if (theTextField == textField) {
[textField resignFirstResponder];
}
return YES;
}


- (void)dealloc {
// To adhere to memory management rules, release the instance variables.
[string release];
[textField release];
[label release];
[super dealloc];
}


@end