1 #import <UIKit/UIKit.h>
2 
3 @interface ViewController : UIViewController
4 @property (weak, nonatomic) IBOutlet UILabel *helloLable;
5 - (IBAction)helloButton:(UIButton *)sender;
6 
7 @end

 1 #import "ViewController.h"
 2 
 3 @interface ViewController ()
 4 
 5 @end
 6 
 7 @implementation ViewController
 8 
 9 - (void)viewDidLoad {
10     [super viewDidLoad];
11     // Do any additional setup after loading the view, typically from a nib.
12     
13 }
14 
15 - (void)didReceiveMemoryWarning {
16     [super didReceiveMemoryWarning];
17     // Dispose of any resources that can be recreated.
18 }
19 
20 - (IBAction)helloButton:(UIButton *)senhder {
21     self.helloLable.frame = CGRectMake(10, 50, 300, 40);
22     self.helloLable.text = @"Hello World!";
23 }
24 @end

1 #import <UIKit/UIKit.h>
2 
3 @interface AppDelegate : UIResponder <UIApplicationDelegate>
4 
5 @property (strong, nonatomic) UIWindow *window;
6 
7 @end

 1 #import "AppDelegate.h"
 2 #import "ViewController.h"
 3 @interface AppDelegate ()
 4 
 5 @end
 6 
 7 @implementation AppDelegate
 8 
 9 
10 - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
11     // Override point for customization after application launch.
12     //创建window
13     self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
14     //创建ViewController实例
15     ViewController *viewController = [[ViewController alloc] initWithNibName:@"HelloWorldView" bundle:nil];
16     //设置window根视图控制器
17     self.window.rootViewController = viewController;
18     self.window.backgroundColor = [UIColor whiteColor];
19     [self.window makeKeyAndVisible];
20     return YES;
21 }