iOS第一款iPhone应用程序

// Header File that provides all UI related items.
#import <UIKit/UIKit.h>

// Forward declaration (Used when class will be defined /imported in future)
@class ViewController;  

// Interface for Appdelegate
@interface AppDelegate : UIResponder <UIApplicationDelegate>

// Property window
@property (strong, nonatomic) UIWindow *window;

// Property Viewcontroller

 @property (strong, nonatomic) ViewController *viewController;
//this marks end of interface
@end

// Imports the class Appdelegate's interface
import "AppDelegate.h"

// Imports the viewcontroller to be loaded
#import "ViewController.h"

// Class definition starts here
@implementation AppDelegate


// Method to intimate us that the application launched successfully
- (BOOL)application:(UIApplication *)application
 didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
   self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

   // Override point for customization after application launch.
   self.viewController = [[ViewController alloc]
   initWithNibName:@"ViewController" bundle:nil];
   self.window.rootViewController = self.viewController;
   [self.window makeKeyAndVisible];
   return YES;
}

- (void)applicationWillResignActive:(UIApplication *)application {
   /* Use this method to release shared resources, save user data,
   invalidate timers, and store enough application state information
   to restore your application to its current state in case it is
   terminated later. If your application supports background
   execution, this method is called instead of
   applicationWillTerminate: when the user quits.*/
}

- (void)applicationWillEnterForeground:(UIApplication *)application {
   /* Called as part of the transition from the background to the
   inactive state. Here you can undo many of the changes made on
   entering the background.*/
}

- (void)applicationDidBecomeActive:(UIApplication *)application {
   /* Restart any tasks that were paused (or not yet started) while
   the application was inactive. If the application was previously in
   the background, optionally refresh the user interface.*/
}

- (void)applicationWillTerminate:(UIApplication *)application {
   /* Called when the application is about to terminate. Save data if
   appropriate. See also applicationDidEnterBackground:. */
}

- (void)applicationWillTerminate:(UIApplication *)application {
   /* Called when the application is about to terminate. Save data if appropriate.
   See also applicationDidEnterBackground:. */
}
@end

#import <UIKit/UIKit.h>

// Interface for class ViewController
@interface ViewController : UIViewController

@end

#import "ViewController.h"

// Category, an extension of ViewController class
@interface ViewController ()

@end

@implementation ViewController  

- (void)viewDidLoad {
   [super viewDidLoad];
   // Do any additional setup after loading the view, typically from a nib.
}

- (void)didReceiveMemoryWarning {
   [super didReceiveMemoryWarning];
   // Dispose of any resources that can be recreated.
}
@end