iOS如何實現傳值－－－協議傳值

B  ----> A 傳值

步驟：

1.寫協議

2.添加代理屬性

3.調用代理人 方法

4.給代理人添加協議

5.設置代理人

6.實現協議方法

代碼例子：

SecondViewController.h

//
//  SecondViewController.h
//  協議傳值
//
//  Created by 薩斯輩的呼喚 on 14-6-13.
//  Copyright (c) 2014年 薩斯輩的呼喚. All rights reserved.
//

#import <UIKit/UIKit.h>

// 1.協議傳值
// 協議由後面的視圖控制器指定
@protocol SecondDelegate <NSObject>

// 傳值協議的方法需要帶一個或多個參數
- (void)passValueWithString:(NSString *)string;
@end
@interface SecondViewController : UIViewController

// 2.設置自己的代理人屬性
@property (nonatomic, assign) id<SecondDelegate> delegate;
@end

SecondViewController.m

//
//  SecondViewController.m
//  協議傳值
//
//  Created by 薩斯輩的呼喚 on 14-6-13.
//  Copyright (c) 2014年 薩斯輩的呼喚. All rights reserved.
//

#import "SecondViewController.h"

@interface SecondViewController ()

@end

@implementation SecondViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    button.frame = CGRectMake(20, 200, 200, 40);
    [button setTitle:@"hello" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(buttonClick:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];
}

- (void)buttonClick:(UIButton *)button
{
    [self.delegate passValueWithString:@"liguicai"];
}

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

FirstViewController.h

//
//  FirstViewController.h
//  協議傳值
//
//  Created by 薩斯輩的呼喚 on 14-6-13.
//  Copyright (c) 2014年 薩斯輩的呼喚. All rights reserved.
//

#import <UIKit/UIKit.h>
#import "SecondViewController.h"

// 4.由第一個viewController 簽訂 第二個viewController的協議
@interface FirstViewController : UIViewController <SecondDelegate>

@end

FirstViewController.m

//
//  FirstViewController.m
//  協議傳值
//
//  Created by 薩斯輩的呼喚 on 14-6-13.
//  Copyright (c) 2014年 薩斯輩的呼喚. All rights reserved.
//

#import "FirstViewController.h"
#import "SecondViewController.h"

@interface FirstViewController ()

@end

@implementation FirstViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(20, 120, 200, 40)];
    label.backgroundColor = [UIColor grayColor];
    label.text = @"adfasdf";
    label.tag = 11111;
    [self.view addSubview:label];
    [label release];
    
    UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    button.frame = CGRectMake(10, 250, 200, 40);
    [button setTitle:@"hello" forState:UIControlStateNormal];
    button.backgroundColor = [UIColor redColor];
    [button addTarget:self action:@selector(buttonClick:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];
    
}

- (void)buttonClick:(UIButton *)btn
{
    SecondViewController *secondVC = [[SecondViewController alloc] init];

    // 5.給第二個viewController 指定代理人
    secondVC.delegate = self;
    [self.navigationController pushViewController:secondVC animated:YES];

    
    [secondVC release];
}
// 6.實現協議方法
- (void)passValueWithString:(NSString *)string
{
    NSLog(@"%@", string);
    UILabel *label = (UILabel *)[self.view viewWithTag:11111];
    label.text= string;
}

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