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：
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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; } |