javascript - 当前 React JS : 'state' is not defined no-undef

Question

我正在学习 ReactJS，我遇到了这个错误 “状态”未定义 no-undef您对哪里出了问题的帮助。我有当前的 React“react”:“^16.8.6”。我尝试添加 this.state 而不是我得到:第 1 行:'Component' 已定义但从未使用过 no-unused-vars第 8 行:不要直接改变状态。使用 setState() react/no-direct-mutation-state

App.js

import React, { Component } from 'react';
import './App.css';
import Todos from './Components/Todos';



function App() {
  state = {
    todos:[
      {
        id:1,
        title: "Study File Structure",
        completed:false
      },
      {
        id:2,
        title: "Create Component",
        completed:false
      },
      {
        id:3,
        title: "Study State",
        completed:false
      }
    ]
  }

  return ( 
    <div className="App">

      <h1>Hello</h1>
      <Todos/>
    </div>
  );
}

export default App;

Answer 1

将 function App() { 替换为 class App extends Component{。这将使您朝着正确的方向前进，并将返回包装在渲染方法中，如下所示:

class App extends Component{
  state = {
    todos:[
      {
        id:1,
        title: "Study File Structure",
        completed:false
      },
      {
        id:2,
        title: "Create Component",
        completed:false
      },
      {
        id:3,
        title: "Study State",
        completed:false
      }
    ]
  }

  render(){
    return ( 
      <div className="App">

        <h1>Hello</h1>
        <Todos/>
      </div>
    );
  }
}

export default App;