五年后，随着 React Hooks 的推出，现在有了更优雅的使用 useContext hook 的方法。
您在全局范围内定义上下文，在父组件中导出变量、对象和函数，然后将应用程序中的子组件包装在提供的上下文中，并在子组件中导入您需要的任何内容。下面是一个概念证明。
import React, { useState, useContext } from "react";
import ReactDOM from "react-dom";
import styles from "./styles.css";
// Create context container in a global scope so it can be visible by every component
const ContextContainer = React.createContext(null);
const initialAppState = {
selected: "Nothing"
};
function App() {
// The app has a state variable and update handler
const [appState, updateAppState] = useState(initialAppState);
return (
<div>
<h1>Passing state between components</h1>
{/*
This is a context provider. We wrap in it any children that might want to access
App's variables.
In 'value' you can pass as many objects, functions as you want.
We wanna share appState and its handler with child components,
*/}
<ContextContainer.Provider value={{ appState, updateAppState }}>
{/* Here we load some child components */}
<Book title="GoT" price="10" />
<DebugNotice />
</ContextContainer.Provider>
</div>
);
}
// Child component Book
function Book(props) {
// Inside the child component you can import whatever the context provider allows.
// Earlier we passed value={{ appState, updateAppState }}
// In this child we need the appState and the update handler
const { appState, updateAppState } = useContext(ContextContainer);
function handleCommentChange(e) {
//Here on button click we call updateAppState as we would normally do in the App
// It adds/updates comment property with input value to the appState
updateAppState({ ...appState, comment: e.target.value });
}
return (
<div className="book">
<h2>{props.title}</h2>
<p>${props.price}</p>
<input
type="text"
//Controlled Component. Value is reverse vound the value of the variable in state
value={appState.comment}
onChange={handleCommentChange}
/>
<br />
<button
type="button"
// Here on button click we call updateAppState as we would normally do in the app
onClick={() => updateAppState({ ...appState, selected: props.title })}
>
Select This Book
</button>
</div>
);
}
// Just another child component
function DebugNotice() {
// Inside the child component you can import whatever the context provider allows.
// Earlier we passed value={{ appState, updateAppState }}
// but in this child we only need the appState to display its value
const { appState } = useContext(ContextContainer);
/* Here we pretty print the current state of the appState */
return (
<div className="state">
<h2>appState</h2>
<pre>{JSON.stringify(appState, null, 2)}</pre>
</div>
);
}
const rootElement = document.body;
ReactDOM.render(<App />, rootElement);
您可以在代码沙盒编辑器中运行此示例。
