Controller之間傳遞數據：協議傳值

http://itjoy.org/?p=416

 

      前邊介紹過從第一個頁面傳遞數據到第二個頁面，那麼反過來呢咱們該如何操做？仍是同一個例子，將第二個頁面的字符串傳遞到第一個頁面顯示出來，這中形式就能夠使用協議來傳值，協議咱們能夠理解成雙方規定好一組標準，都知足這個標準咱們之間就能夠通訊，一方經過協議發送數據，另外一方經過協議來接受數據。

 

代碼以下：從Second傳遞數據到First

 

 

 

 

 

 

Objective-C

 

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///////////////////////// /////////FirstViewController.h//////////// #import <UIKit/UIKit.h> #import "SecondViewController.h"   @interface FirstViewController : UIViewController<UITextFieldDelegate,SendMessage>  //遵照SendMessage協議 @property (nonatomic, retain) UILabel *nameLable; @end   ///////////FirstViewController.m - (void)viewDidLoad {     [super viewDidLoad];          self.nameLable = [[[UILabel alloc]initWithFrame:CGRectMake(10, 10, 300, 60)]autorelease];     self.nameLable.textAlignment = UITextAlignmentCenter;     self.nameLable.font = [UIFont systemFontOfSize:50];     self.nameLable.textColor = [UIColor blueColor];     [self.view addSubview:self.nameLable];            UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];     button.frame = CGRectMake(130, 170, 60, 40);     [button setTitle:@"下一個" forState:UIControlStateNormal];     [button addTarget:self action:@selector(pushNext:) forControlEvents:UIControlEventTouchUpInside];     [self.view addSubview:button]; }   - (void)pushNext:(id)sender {     //初始化second     SecondViewController *second = [[SecondViewController alloc]init];     //設置代理，由誰去執行     second.delegate = self;     //推過去     [self.navigationController pushViewController:second animated:YES];     [second release]; } //實現協議的方法 - (void)sendValue:(NSString *)str {     //賦值操做     self.nameLable.text = str; }

 

 

 

 

 

 

 

Objective-C

 

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//////////////////////// //////////////////SecondViewController.h #import <UIKit/UIKit.h> @protocol SendMessage;   @interface SecondViewController : UIViewController<UITextFieldDelegate> @property(nonatomic, assign)id<SendMessage> delegate; @end   ///協議的定義，包含一個方法。 @protocol SendMessage <NSObject>   - (void)sendValue:(NSString *)str;   @end /////////////SecondViewController.m - (void)viewDidLoad {     [super viewDidLoad];          UITextField *textFd = [[UITextField alloc]initWithFrame:CGRectMake(10, 10, 300, 150)];     textFd.borderStyle = UITextBorderStyleRoundedRect;     textFd.delegate = self;     textFd.tag = 100;     [self.view addSubview:textFd];     [textFd release]; }   - (BOOL)textFieldShouldReturn:(UITextField *)textField {     [textField resignFirstResponder];     //若是delegate 是這個類型的就調用這個方法，相似於java中的接口，子類實現接口，能夠調用接口中的方法     if ([self.delegate conformsToProtocol:@protocol(SendMessage) ]) {         [self.delegate sendValue:textField.text];     }     return YES; }