ios 得用代理反向传值

   应用场景：有时时候从界面A跳转到界面B,界面B在返回的时候须要将处理的结果传递给A.

   实现思路：1，定义一个负责传值的协义，界面A拥有该协义属性，并实现该协义中的方法

                       2。界面B也拥有该协义属性（代理要求两者都具有同样对象的引用 ），然后在返回的时候获取界面A的引用指针，而且指定B中协义的调用目标为A,调用协义中的传值方法.

 详细代码:

    A的头文件 ：

#import <UIKit/UIKit.h>

@protocol passValueDelegate <NSObject>

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

@end

@interface ViewController : UIViewController

@property id<passValueDelegate> passValueDelegate;

@end

  A的实现文件 :

 

#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的头文件 ：

 

#import <UIKit/UIKit.h>

@interface ViewController2 : UIViewController

@end

B的实现文件:

#import "ViewController2.h"

#import "ViewController.h"

@interface ViewController2 ()

@property id<passValueDelegate> 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