Controller之间传递数据：Block传值

http://itjoy.org/?p=420

前边我们介绍过属性传值和协议传值，这里介绍一下块传值，块类似于C中的函数指针。在Controller中传递数据非常方便，还是继续上一章的例子，将数据从Second传递到First，这里使用块来完成,看起来似乎和协议很像，不过比协议略简单。

代码如下所示：

 

 

 

 

 

Objective-C

 

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/////////// ////////FirstViewController - (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:@"下一个" 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];     ///调用块     second.send = ^(NSString *str){         self.nameLable.text = str;     };     //推过去     [self.navigationController pushViewController:second animated:YES];     [second release]; }

 

 

 

 

 

Objective-C

 

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///////////// ////////////SecondViewController.h #import <UIKit/UIKit.h> typedef  void (^SendMessage) (NSString *str); ///声明块   @interface SecondViewController : UIViewController<UITextFieldDelegate> @property (nonatomic, copy) SendMessage send;  //声明一个块类型属性 @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];     //先判断，在调用块传递实参     if (self.send) {         self.send (textField.text);     }     return YES; }