Block传值

页⾯间的传值，有层级正向和逆向传值。正向传值⼀般⽤属性传值即可。逆向传值有代理传值和我们的block传值。

//
//  FirstViewController.m
//  Block传值
//
//  Created by cqy on 16/2/16.
//  Copyright © 2016年 程清杨. All rights reserved.
//

#import "FirstViewController.h"

@interface FirstViewController (){
    UITextField *field;
}


@end

@implementation FirstViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.title = @"block";
    self.navigationController.navigationBar.barTintColor = [UIColor redColor];
   
    field = [[UITextField alloc] initWithFrame:CGRectMake(20, 80, 300, 40)];
    field.borderStyle = UITextBorderStyleRoundedRect;
    [self.view addSubview:field];
    self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc]initWithTitle:@"next" style:(UIBarButtonItemStyleDone) target:self action:@selector(rightAction:)];
   

    // Do any additional setup after loading the view.
}
- (void)rightAction:(UIBarButtonItem *)sender{
    //响应⽅法中，实现我们再Second视图控制器中声明的block 。这个block再这⾥实现，在Second视图中调⽤，传进来⼀个参数，那个参数就是我们再second视图想要再视图显⽰的数据。这⾥就是str。
   
    SecondViewController *SecondView = [[SecondViewController alloc]init];
    // 给second传值
    SecondView.Str = field.text;
    // 执⾏再second调⽤的block，赋值给first
    SecondView.mb = ^(NSString *str){
        field.text = str;
    };
    [self.navigationController pushViewController:SecondView animated:YES];
  
   
}

- (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

 

//
//  SecondViewController.h
//  Block传值
//
//  Created by cqy on 16/2/16.
//  Copyright © 2016年 程清杨. All rights reserved.
//

#import <UIKit/UIKit.h>
// 给⼀个block取名为MyBlock，参数是NSString类型的。
typedef void (^MyBlock)(NSString *str);
@interface SecondViewController : UIViewController

@property(nonatomic,copy) NSString *Str;
// 定义⼀个block属性
//在这⾥声明⼀个block变量mb。为的是再其他类中可以⽤到。
@property(nonatomic,copy)MyBlock mb;

@end

//
//  SecondViewController.m
//  Block传值
//
//  Created by cqy on 16/2/16.
//  Copyright © 2016年 程清杨. All rights reserved.
//

#import "SecondViewController.h"
@interface SecondViewController (){
    UITextField *field;
}

@end

@implementation SecondViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor lightGrayColor];
   
    field = [[UITextField alloc] initWithFrame:CGRectMake(20, 80, 300, 40)];
    field.borderStyle = UITextBorderStyleRoundedRect;
    [self.view addSubview:field];
    self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc]initWithTitle:@"on" style:(UIBarButtonItemStyleDone) target:self action:@selector(leftAction:)];
   
   
    // Do any additional setup after loading the view.
}
- (void)leftAction:(UIBarButtonItem *)sender{
    // pop之前，调⼀个block传值
    self.mb(field.text);//这⾥调⽤block将field的值作为参数，去到first视图控制器中执⾏。就能实现把值传给上级视图的需求。
    [self.navigationController popToRootViewControllerAnimated:YES];
}
- (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