應用場景：有時時候從界面A跳轉到界面B,界面B在返回的時候需要將處理的結果傳遞給A.

實現思路：1，定義一個負責傳值的協義，界面A擁有該協義屬性，並實現該協義中的方法

2，界面B也擁有該協義屬性（代理要求兩者都具有相同對象的引用 ），然後在返回的時候獲取界面A的引用指針，並且指定B中協義的調用目標為A,調用協義中的傳值方法.

具體代碼:

A的頭文件 ：

#import

@protocol passValueDelegate

-(void) setValue:(NSString *)param;

@end

@interface ViewController : UIViewController

@property id passValueDelegate;

@end

A的實現文件 :

#import "ViewController.h"

#import "ViewController2.h"

@interface ViewController ()

{

}

@end

@implementation ViewController

- (void)viewDidLoad

{

[super viewDidLoad];

// Do any additional setup after loading the view, typically from a nib.

UIButton *btn =[UIButton buttonWithType:UIButtonTypeRoundedRect];

btn.frame=CGRectMake(100, 100, 200, 40);

[btn setTitle:@"btn" forState:UIControlStateNormal];

[btn addTarget:self action:@selector(btn) forControlEvents:UIControlEventTouchUpInside];

[self.view addSubview:btn];

self.view.backgroundColor=[UIColor redColor];

}

-(void) setValue:(NSString *)param{

NSLog(@"pass value is:%@",param);

}

-(void)btn

{

[self.navigationController pushViewController:[[ViewController2 alloc]init] animated:YES];

}

- (void)didReceiveMemoryWarning

{

[super didReceiveMemoryWarning];

// Dispose of any resources that can be recreated.

}

@end

B的頭文件 ：

#import

@interface ViewController2 : UIViewController

@end

B的實現文件:

#import "ViewController2.h"

#import "ViewController.h"

@interface ViewController2 ()

@property id passValueDelegate;

@end

@implementation ViewController2

- (void)viewDidLoad

{

[super viewDidLoad];

UIButton *btn =[UIButton buttonWithType:UIButtonTypeRoundedRect];

btn.frame=CGRectMake(100, 100, 200, 40);

[btn setTitle:@"back" forState:UIControlStateNormal];

[btn addTarget:self action:@selector(btn) forControlEvents:UIControlEventTouchUpInside];

[self.view addSubview:btn];

}

-(void)btn

{

// NSLog(@"%@",self.navigationController.childViewControllers[0]);

self.passValueDelegate=self.navigationController.childViewControllers[0];

[self.navigationController popToRootViewControllerAnimated:YES];

[self.passValueDelegate setValue:@"123456789"];

}

- (void)didReceiveMemoryWarning

{

[super didReceiveMemoryWarning];

// Dispose of any resources that can be recreated.

}

@end