控制器之间的数据传递——Block传值

Block传值

我们先在这里约定：界面1传值到界面2为顺传，界面2传值到界面1为逆传

一般用Block传值是为了降低视图控制器之间的耦合度，和代理传值类似主要用于逆序传值。

一. 实现步骤

1. 给界面2定义一个Block属性；注意：在block传值中，要传几个值，block就有几个参数，参数要与传的值对应

2. 在界面2的跳转方法中检查block属性是否有值，有值就执行block，然后界面2出栈

3. 在界面1的跳转方法中创建界面2，并把要执行的赋值语句保存到界面2的block变量属性

二. 具体代码

1. AppDelegate类

---------- AppDelegate.m文件

#import "AppDelegate.h"
#include "OneViewController.h"

@interface AppDelegate ()

@end

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

  // 1. 创建窗口
  self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];

  // 2. 创建窗口的根控制器
  // 2.1 创建导航控制器的根控制器
  UIViewController *oneVc = [[OneViewController alloc] init];
  // 2.2 创建导航控制器
  UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController:oneVc];
  // 2.3 给窗口设置根控制器
  self.window.rootViewController = nav;

  // 3. 设置窗口为主窗口并显示窗口
  [self.window makeKeyAndVisible];

  // 隐藏导航控制器的导航条
  nav.navigationBarHidden = YES;

  return YES;
}

@end

2. OneViewController类

---------- OneViewController.m文件

#import "OneViewController.h"
#import "TwoViewController.h"

@interface OneViewController ()

@property (nonatomic,strong) UITextField *textField;

@end

@implementation OneViewController

- (void)viewDidLoad {
  [super viewDidLoad];

  //设置控制器View的背景颜色
  self.view.backgroundColor = [UIColor greenColor];

  // 创建点击按钮
  UIButton *clickBtn = [UIButton buttonWithType:UIButtonTypeCustom];
  clickBtn.frame = CGRectMake(10, 100, 80, 40);
  clickBtn.backgroundColor = [UIColor whiteColor];
  [clickBtn setTitle:@"到界面2" forState:UIControlStateNormal];
  [clickBtn setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
  [clickBtn setTitleColor:[UIColor redColor] forState:UIControlStateHighlighted];
  [clickBtn addTarget:self action:@selector(btnClick) forControlEvents:UIControlEventTouchUpInside];
  [self.view addSubview:clickBtn];

  // 创建文本框
  _textField = [[UITextField alloc] initWithFrame:CGRectMake(10, 150, 250, 40)];
  _textField.borderStyle = UITextBorderStyleRoundedRect;
  _textField.backgroundColor = [UIColor whiteColor];
  [self.view addSubview:_textField];

}

#pragma mark - 点击事件

- (void)btnClick {

  // 创建界面2，并压入栈
  TwoViewController *twoVc = [[TwoViewController alloc] init];
  [self.navigationController pushViewController:twoVc animated:YES];

  // 给界面的Block设置传值代码块
  twoVc.twoBlock = ^(NSString *str){
    // 用界面2的值赋给界面1的文本框，这句代码是在界面1中执行的
    _textField.text = str;
  };

}

@end

3. TwoViewController类

---------- TwoViewController.h文件

#import <UIKit/UIKit.h>

// 自定义一个Block变量类型名
typedef void(^TwoViewControllerBlock)(NSString *);

@interface TwoViewController : UIViewController

// Block属性
@property (nonatomic,strong) TwoViewControllerBlock twoBlock;

@end

---------- TwoViewController.h文件

#import "TwoViewController.h"

@interface TwoViewController ()

@property (nonatomic,strong) UITextField *textField;

@end

@implementation TwoViewController

- (void)viewDidLoad {
    [super viewDidLoad];

  //设置控制器View的背景颜色
  self.view.backgroundColor = [UIColor yellowColor];

  // 创建点击按钮
  UIButton *clickBtn = [UIButton buttonWithType:UIButtonTypeCustom];
  clickBtn.frame = CGRectMake(10, 100, 80, 40);
  clickBtn.backgroundColor = [UIColor whiteColor];
  [clickBtn setTitle:@"传 值" forState:UIControlStateNormal];
  [clickBtn setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
  [clickBtn setTitleColor:[UIColor redColor] forState:UIControlStateHighlighted];
  [clickBtn addTarget:self action:@selector(btnClick) forControlEvents:UIControlEventTouchUpInside];
  [self.view addSubview:clickBtn];

  // 创建文本框
  _textField = [[UITextField alloc] initWithFrame:CGRectMake(10, 150, 250, 40)];
  _textField.borderStyle = UITextBorderStyleRoundedRect;
  _textField.backgroundColor = [UIColor whiteColor];
  [self.view addSubview:_textField];
}

#pragma mark - 点击事件

- (void)btnClick {

  // 如果Block有值就执行Block
  if (_twoBlock) {
    // 传入文本框的值传到界面1
    _twoBlock(_textField.text);
  }

  // 跳转界面
  [self.navigationController popViewControllerAnimated:YES];

}

@end