使用React Hooks时，TypeError dispatcher.useState不是函数 [英] TypeError dispatcher.useState is not a function when using React Hooks

问题描述

我有这个组件：

import React, { useState, useEffect } from "react";
import ReactDOM from "react-dom";

function App() {
  const [count, setCount] = useState(0);
  useEffect(() => {
    document.title = `You clicked ${count} times`;
  });

  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={() => setCount(count + 1)}>Click me</button>
    </div>
  );
}

export default App;

因为我想尝试新的中安装 react@16.8.1 ，docs / hooks-intro.htmlrel =nofollow noreferrer> React hooks 提案package.json ，但是我收到一个错误：

as I want to try out the new React hooks proposal by installing react@16.8.1 in my package.json, but I'm getting an error:

TypeError: dispatcher.useState is not a function

  2 | import ReactDOM from "react-dom";
  3 | 
  4 | function App() {
> 5 |   const [count, setCount] = useState(0);
    |                                     ^
  6 |   useEffect(() => {
  7 |     document.title = `You clicked ${count} times`;
  8 |   });

我做错了什么？

推荐答案

可能有很多原因，大多数是由于版本不兼容或在 package.json中使用 ^ ：

There could be many reasons, and most are due to version incompatibilites or using a ^ in package.json:

1. 确保您还更新了 react-dom 包，与相同的版本 。通常 react 和 react-dom 应该始终是 package.json中的相同版本当React团队一起更新它们。

1. Ensure that you have also updated the react-dom package and it is of the same version as react. In general react and react-dom should always be the same version in package.json as the React team updates them together.

如果你想安装React 16.7.0-alpha.2 ，检查您是否使用 ^ ，因为您将安装16.7而不是挂钩。

If you want to install React 16.7.0-alpha.2, check that you are not using the ^ as you will install 16.7 instead, which doesn't have hooks.

示例 package.json ：

{
  ...
  "dependencies": {
    "react": "16.8.1", // Make sure version is same as react-dom
    "react-dom": "16.8.1",
    ...
  }
}

---

---

1. 如果您使用的是Jest，请确保 react-test-renderer 版本与反应和 react-dom ：

1. If you are using Jest, ensure that react-test-renderer is of the same version as react and react-dom:

示例 package.json ：

{
  ...
  "dependencies": {
    "react": "16.8.1",
    "react-dom": "16.8.1",
    "react-test-renderer": "16.8.1",
    ...
  }
}

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