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
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
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
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