IOS学习之——ViewController之间双向传值（反向为代理模式）

下面的代码如下，正向传值是用普通的传值模式，反向传值用的是代理模式。实现代理模式的步骤如下：

代理方:

1.遵守原则 (遵守协议)

2.实现代理方法 (实现协议中的方法)

3.设置委托方的代理人

委托方 :

1.制定原则 (协议)

2.声明代理的属性（协议类型的属性） delegate

3.在适当的时机，让代理人执行代理方法 (delegate调用协议中的方法)

第一个界面的头文件和实现文件如下：

#import <UIKit/UIKit.h>

@interface OneViewController : UIViewController

@end

//
//  OneViewController.m
//  双向传值
//
//  Created by spare on 16/4/16.
//  Copyright © 2016年 spare. All rights reserved.
//
//代理方:
//1.遵守原则 (遵守协议)
//2.实现代理方法 (实现协议中的方法)
//3.设置委托方的代理人
#import "OneViewController.h"
#import "TwoViewController.h"
//1.遵守原则 (遵守协议)
@interface OneViewController ()<TwoDelegate>@property (weak, nonatomic) IBOutlet UITextField *textField1;

@end

@implementation OneViewController

//2.实现代理方法 (实现协议中的方法)
-(void)sendTwoController:(TwoViewController *)twoController message:(NSString *)message{
    //将从页面2返回的值，传到页面1的textField
    self.textField1.text=message;
}


//点击屏幕任意位置，进入页面2
-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
    //初始化将要进入的页面
    TwoViewController *vc2=[[TwoViewController alloc]init];
    //正向传值代码：通过页面2定义的Content属性，将值传给页面2
    vc2.content=self.textField1.text;
    //3.设置委托方的代理人
    //反向传值代码：设置代理（很重要!!!）
    vc2.delegate=self;
    [self presentViewController:vc2 animated:YES completion:nil];
    }

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

/*
#pragma mark - Navigation

// In a storyboard-based application, you will often want to do a little preparation before navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    // Get the new view controller using [segue destinationViewController].
    // Pass the selected object to the new view controller.
}
*/

@end

第二个界面的头文件和实现文件如下：

//  TwoViewController.h
//  双向传值
//
//  Created by spare on 16/4/16.
//  Copyright © 2016年 spare. All rights reserved.
//
////委托方	:
//1.制定原则 (协议)
//2.声明代理的属性 （协议类型的属性） delegate
//3.在适当的时机，让代理人执行代理方法 (delegate 调用协议中的方法)
#import <UIKit/UIKit.h>
@class TwoViewController;
//1.制定原则 (协议)
@protocol TwoDelegate <NSObject>
-(void)sendTwoController:(TwoViewController*)twoController message:(NSString*)message;
@end

@interface TwoViewController : UIViewController

@property(nonatomic,copy)NSString *content;
//2.声明代理的属性 （协议类型的属性） delegate
@property(nonatomic,strong)id<TwoDelegate> delegate;

@end

//
//  TwoViewController.m
//  双向传值
//
//  Created by spare on 16/4/16.
//  Copyright © 2016年 spare. All rights reserved.
//

#import "TwoViewController.h"

@interface TwoViewController ()

@property (weak, nonatomic) IBOutlet UITextField *textField2;

@end

@implementation TwoViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
}

-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
   //3.在适当的时机，让代理人执行代理方法 (delegate 调用协议中的方法)
    [self.delegate sendTwoController:self message:self.textField2.text];
    
    [self dismissViewControllerAnimated:YES completion:nil];
}

//每次进入页面的时候，都去刷新获得的值
-(void)viewWillAppear:(BOOL)animated{
    //通过中间属性，传值给textField2；
    self.textField2.text=self.content;
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

/*
#pragma mark - Navigation

// In a storyboard-based application, you will often want to do a little preparation before navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    // Get the new view controller using [segue destinationViewController].
    // Pass the selected object to the new view controller.
}
*/

@end