控制器之间的数据传递——全局变量传值

全局变量传值

一. 实现步骤

1. 在界面2中声明一个全局变量，并且用它保存需要传递的值

2. 在界面1中用extern声明界面2中的全局变量，就可使用他所保存的值赋值

二. extern优缺点

1. 优点

   a.全局可视，任何一个函数都可以访问和更改变量值
   b.内存地址固定，读写效率高

2. 缺点

   a.容易造成命名冲突
   b.当值不正确或者出错时，很难确定是哪个函数更改过这个变量
   c.不支持多线程

三. 具体实现

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"// 必须要用extern关键字修饰，才能使用extern NSString *PassData;@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];}- (void)viewWillAppear:(BOOL)animated {  _textField.text = PassData;}@end

3. TwoViewController类

---------- TwoViewController.m文件#import "TwoViewController.h"// 设置全局变量，用于在不同的文件中传值NSString *PassData;@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 {  PassData = _textField.text;  // 跳转界面  [self.navigationController popViewControllerAnimated:YES];}@end