Dart 中的全局变量 [英] Global Variables in Dart

问题描述

我尝试创建一个 Dart 单页应用程序.

I try to create a Dart single page application.

我创建了第一个包含整个应用程序的自定义元素 (custom-application).它有一个用于渲染视图的容器.以及包含用户信息并在用户登录时更新的侧边导航.

I have created a first custom element (custom-application) which contains the whole application. It has a container in it which is used to render views. And a side nav which will contain user informations and be updated when the user is log in.

我想在视图之间共享信息.如何在 custom-application 中定义全局变量并能够与其他视图共享?

I want to share informations between views. How can I define a global variable in custom-application and be able to share it with the other views ?

例如，当您启动应用程序时，您未经过身份验证.当您调用/login (login-view) 时，您将获得一个登录表单.我希望，当您登录应用程序时，custom-application 元素存储由嵌套视图 login-view 加载的用户信息并更新侧导航.

For example, when you start the app, you are not authenticated. When you call /login (login-view) you'll have a login form. I want, when you log in the application, the custom-application element stores the user informations loaded by the nested view login-view and update the side nav.

可以吗?

推荐答案

只需创建一个库文件并为您需要的全局变量创建字段即可.在需要访问这些字段的任何位置导入此库.

Just create a library file and create fields for globals you need there. Import this library everywhere you need access to these fields.

app.dart

import 'globals.dart' as globals;

main() {
  globals.isLoggedIn = true;
}

component1.dart

import 'globals.dart' as globals;

class MyComponent {
  view() {
    if(globals.isLoggedIn) {
      doSomething();
    else {
      doSomethingElse();
    }
  }
}

globals.dart

library my_prj.globals;

bool isLoggedIn = false;

你也可以

• 在 globals 库中创建一个单例(请参阅如何在 Dart 中构建单例?了解更多详情).
• 使用 observable 获取有关更改的通知(请参阅在 Dart 中实现观察者模式、如何在类中触发一种 onChange 事件 了解更多详情)

• create a singleton in the globals library (see How do you build a Singleton in Dart? for more details).
• use observable to get notified about changes (see Implement an Observer pattern in Dart, How can i trigger a kind of onChange event in a class for more details)

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