Block传值

其实block传值个人感觉跟代理很相似.也是从后往前传.

//流程:
1.后一个界面定义一个block,并且定义一个属性block
2.在后一个界面返回前一个界面的瞬间,(即:创建完成一个界面之后),调用block;
3.前一个界面实现block的实现
4.后一个界面在合适的机会, 让(传的值以参数的形式 含在block的参数里)

 

代码如下： 

//
//  ViewController.h
//  Block传值
//
//  Created by luoyin on 15/4/23.
//  Copyright (c) 2015年 luoyin. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController


@end

//
//  ViewController.m
//  Block传值
//
//  Created by luoyin on 15/4/23.
//  Copyright (c) 2015年 luoyin. All rights reserved.
//

#import "ViewController.h"
#import "SecondViewController.h"

@interface ViewController ()
@property (nonatomic, strong) UILabel *label;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    self.navigationItem.title = @"第一个页面";
    self.view.backgroundColor = [UIColor grayColor];
    
    //添加按钮,跳转到下一个页面
    CGFloat mainscreen = [UIScreen mainScreen].bounds.size.width;
    UIButton *button = [[UIButton alloc]initWithFrame:CGRectMake(100, 160, mainscreen -200, 40)];
    [button setTitle:@"下一页" forState:UIControlStateNormal];
    button.backgroundColor = [UIColor blueColor];
    [button addTarget:self action:@selector(nextView:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];
    
    //创建一个label,显示第二个页面传过来的值
    _label = [[UILabel alloc]initWithFrame:CGRectMake(40, 100, mainscreen-80, 40)];
    _label.textAlignment = NSTextAlignmentCenter;
    _label.text = @"等待第二个页面Block传值";
    _label.backgroundColor = [UIColor yellowColor];
    _label.textColor = [UIColor grayColor];
    [self.view addSubview:_label];
    
}

- (void)nextView:(UIButton *)button{
    
    button.backgroundColor = [UIColor redColor];
    SecondViewController *secondView = [[SecondViewController alloc]init];
    
    //把第二页输入框输入的字符串,通过block内部实现传过来
    secondView.block = ^(NSString *string){
        _label.text = string;
    };
    [self.navigationController pushViewController:secondView animated:NO];
}

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

@end

//
//  SecondViewController.h
//  Block传值
//
//  Created by luoyin on 15/4/23.
//  Copyright (c) 2015年 luoyin. All rights reserved.
//

#import <UIKit/UIKit.h>

typedef void(^secondViewBlock)(NSString *string);
@interface SecondViewController : UIViewController

@property (nonatomic, copy)secondViewBlock block;

@end

//
//  SecondViewController.m
//  Block传值
//
//  Created by luoyin on 15/4/23.
//  Copyright (c) 2015年 luoyin. All rights reserved.
//

#import "SecondViewController.h"

@interface SecondViewController ()

@property (nonatomic, strong) UITextField *textField;

@end

@implementation SecondViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    self.navigationItem.title = @"第二个页面";
    self.view.backgroundColor = [UIColor grayColor];
    
    CGFloat mainscreen = [UIScreen mainScreen].bounds.size.width;
    _textField = [[UITextField alloc]initWithFrame:CGRectMake(40, 100, mainscreen-80, 40)];
    _textField.placeholder = @"请输入返回第一个页面的内容";
    _textField.textAlignment = NSTextAlignmentCenter;
    _textField.backgroundColor = [UIColor whiteColor];
    [self.view addSubview:_textField];
    
    //配置navigationController
    self.navigationItem.leftBarButtonItem = ({
        UIButton *button = [[UIButton alloc]initWithFrame:CGRectMake(0, 0, 40, 40)];
        [button setTitle:@"返回" forState:UIControlStateNormal];
        button.tintColor = [UIColor blackColor];
        [button setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
        [button addTarget:self action:@selector(backToFistView:) forControlEvents:UIControlEventTouchUpInside];
        UIBarButtonItem *buttonItem = [[UIBarButtonItem alloc]initWithCustomView:button];
        buttonItem;
    });
}

- (void)backToFistView:(UIButton *)button{
    
    //调用block方法,把_textField.text参数传过去
    _block(_textField.text);
    [self.navigationController popViewControllerAnimated:NO];
}

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

@end

 测试结果如下：