1 #import <Foundation/Foundation.h> 2  3 @interface AppStatus : NSObject 4 { 5     NSString *_contextStr; 6 } 7  8 @PRoperty(nonatomic,retain)NSString *contextStr; 9 10 +(AppStatus *)shareInstance;11 12 @end

 1 #import "AppStatus.h" 2  3 @implementation AppStatus 4  5 @synthesize contextStr = _contextStr; 6  7 static AppStatus *_instance = nil; 8  9 +(AppStatus *)shareInstance10 {11     if (_instance == nil)12     {13         _instance = [[super alloc]init];14     }15     return _instance;16 }17 18 -(id)init19 {20     if (self = [super init])21     {22         23     }24     return self;25 }26 27 -(void)dealloc28 {29     [super dealloc];30 }31 32 @end

 1 #import "RootViewController.h" 2 #import "DetailViewController.h" 3 #import "AppStatus.h" 4  5 @interface RootViewController () 6  7 @end 8  9 @implementation RootViewController10 11 -(void)loadView12 {13     //核心代碼 14     UIButton *btn = [UIButton buttonWithType:UIButtonTypeRoundedRect];15     btn.frame = CGRectMake(0, 0, 100, 30);16     [btn setTitle:@"Push" forState:0];17     [btn addTarget:self action:@selector(pushAction:) forControlEvents:UIControlEventTouchUpInside];18     [self.view addSubview:btn];19 }20 21 -(void)pushAction:(id)sender22 {23     tf = (UITextField *)[self.view viewWithTag:1000];24 25  //單例傳值  將要傳遞的信息存入單例中（共享中）26   //  [[AppStatus shareInstance]setContextStr:tf.text]; 跟下面這種寫法是等價的27     [AppStatus shareInstance].contextStr = tf.text;28     //導航push到下一個頁面29     //pushViewController 入棧引用計數+1，且控制權歸系統30     DetailViewController *detailViewController = [[DetailViewController alloc]init];31 32     //導航push到下一個頁面33     [self.navigationController pushViewController:detailViewController animated:YES];34     [detailViewController release];35 } 36 37 @end

1 #import <UIKit/UIKit.h>2 @protocol ChangeDelegate;//通知編譯器有此代理3 4 @interface DetailViewController : UIViewController5 {6     UITextField *textField;7 }8 9 @end

 1 #import "DetailViewController.h" 2 #import "AppStatus.h" 3  4 @interface DetailViewController () 5  6 @end 7  8 @implementation DetailViewController 9 10 @synthesize naviTitle = _naviTitle;11 12 -(void)loadView13 {14     self.view = [[[UIView alloc]initWithFrame:CGRectMake(0, 0, 320, 480)]autorelease];15 16     //單例17     self.title = [AppStatus shareInstance].contextStr;18     textField = [[UITextField alloc]initWithFrame:CGRectMake(100, 100, 150, 30)];19     textField.borderStyle = UITextBorderStyleLine;20     [self.view addSubview:textField];21     [textField release];22 23     UIBarButtonItem *doneItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemDonetarget:self action:@selector(doneAction:)];24     self.navigationItem.rightBarButtonItem = doneItem;25     [doneItem release];26 }27 28 //這個方法是執行多遍的  相當于刷新view29 -(void)viewWillAppear:(BOOL)animated30 {31     [super viewWillAppear:animated];32     tf = (UITextField *)[self.view viewWithTag:1000];33     tf.text = [AppStatus shareInstance].contextStr;34 }35 36 //pop回前一個頁面37 -(void)doneAction:(id)sender38 {39     //單例傳值40     [AppStatus shareInstance].contextStr = textField.text;41     [self.navigationController popToRootViewControllerAnimated:YES];42 }