SecondViewController.h

#warning第一步

//在第二個頁面里聲明block屬性

@property(nonatomic,copy)void(^secondBlock)(NSString*str);

SecondViewController.m

-(void)didClickButton:(UIButton*)button{

#warning第二步

//在第二個頁面里執行block回調,將@"路飛"傳給第一個頁面

self.secondBlock(@"路飛");

[self.navigationControllerpopViewControllerAnimated:YES];

}

RootViewController.m

-(void)didClickButton:(UIButton*)button{

SecondViewController* sec = [[SecondViewControlleralloc]init];

#warning第三步

//在第一個頁面中實現block

//block回調

//得到block回傳的string并賦給label

sec.secondBlock= ^(NSString* string){

self.label.text= string;

};

[self.navigationControllerpushViewController:secanimated:YES];

}

SecondViewController.m

-(void)dealloc{

#warning第四步

//Block釋放

Block_release(_secondBlock);

[_textFieldrelease];

[superdealloc];

}