塊傳值，塊類似於C中的函數指針。在Controller中傳遞數據非常方便，還是繼續上一章的例子，將數據從Second傳遞到First，這裡使用塊來完成,看起來似乎和協議很像，不過比協議略簡單。
代碼如下所示：
///////////
////////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];
///調用塊
second.send = ^(NSString *str){
self.nameLable.text = str;
};
//推過去
[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); ///聲明塊
@interface SecondViewController : UIViewController<UITextFieldDelegate>
@property (nonatomic, copy) SendMessage send; //聲明一個塊類型屬性
@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];
//先判斷，在調用塊傳遞實參
if (self.send) {
self.send (textField.text);
}
return YES;
}
