上下文中的提供者值不会改变

Question

我正在尝试在新的 react+typescript 示例项目中学习 ContextAPI。

我想管理语言环境/身份验证。

我必须初始化我的上下文值（Typescript / eslint 需要），特别是 login/logout 函数，或者 "App.tsx" 中发生错误："cannot invoke an object which is possible undefined".

是的，我尝试按如下方式初始化我的上下文：

const AuthContext = React.createContext<ContextProps>({
    ...initialState,
    login: () => {
        throw new Error("login() not implemented yet");
    },
    logout: () => {
        throw new Error("logout() not implemented yet");
    }
 });

现在的问题是，当我定义 login/logout 函数并将其作为值传递给我的提供商时，我的按钮会抛出 "login not implemented yet" 错误。

这是我的代码：

// ./App.tsx
import React from "react";
import { NavItem, Button } from "reactstrap";

import * as Context from "./contexts";

const App = () => {
      return (
      <Context.Language.Consumer>
        {({ locale, translation, switchLocale }) => (
            <Context.Auth.Consumer>
              {Auth => (
                  <NavItem right>
                    {Auth.isLoggedIn ? (
                        <Button onClick={() => Auth.logout()}>
                          {translation.logout}
                        </Button>
                    ) : (
                        <Button onClick={() => Auth.login()}>
                          {translation.login}
                        </Button>
                    )}
                  </NavItem>
              )}
            </Context.Auth.Consumer>
        )}
      </Context.Language.Consumer>
  );
};

export default App;

--

// ./contexts/AuthContext.tsx
import React, {Component} from "react";

type ContextProps = {
  isLoggedIn: boolean;
  login: () => void;
  logout: () => void;
};

const initialState = { isLoggedIn: false };
type Props = {};
type State = {} & typeof initialState;

const AuthContext = React.createContext<ContextProps>({
  ...initialState,
  login: () => {
    throw new Error("login() not implemented yet");
  },
  logout: () => {
    throw new Error("logout() not implemented yet");
  }
});

class AuthProvider extends Component<Props, State> {
   readonly state = initialState;

  login = () => {
    this.setState({
      isLoggedIn: true
    });
  };

  logout = () => {
    this.setState({
      isLoggedIn: false
    });
  };

  render() {
    return (
      <AuthContext.Provider
        value={{...this.state, login: this.login, logout: this.logout}}
      >
        {this.props.children}
      </AuthContext.Provider>
    );
  }
}

export const Consumer = AuthContext.Consumer;
export const Provider = AuthProvider;

最后：

// ./contexts/index.js
import * as Auth from "./AuthContext";
import * as Language from "./LanguageContext";

export { Auth, Language };

似乎新的 login/logout 定义没有传递给 AuthContext 中的提供者。我很确定我错过了 ContextAPI 中的一个概念，而且我不理解背后的逻辑。谢谢你的建议。

Answer 1

您需要添加具有新上下文的提供者。 React 将在树上查找第一个上下文提供者，如果没有，消费者将获得默认值。

const App = () => {
  return (
  <Context.Language.Consumer>
    {({ locale, translation, switchLocale }) => (
       <Context.Auth.Provider>
          <Context.Auth.Consumer>
            {Auth => (
                <NavItem right>
                  {Auth.isLoggedIn ? (
                      <Button onClick={() => Auth.logout()}>
                        {translation.logout}
                      </Button>
                  ) : (
                      <Button onClick={() => Auth.login()}>
                        {translation.login}
                      </Button>
                  )}
                </NavItem>
            )}
        </Context.Auth.Consumer>
      <Context.Auth.Provider>
    )}
  </Context.Language.Consumer>

); };

上下文中的提供者值不会改变

Provider from context value doesn't change

typescript

reactjs

react-context