反应:未捕获的TypeError:无法读取未定义的属性“状态" [英] react: uncaught TypeError: Cannot read property 'state' of undefined

问题描述

我正在尝试从通用类中获取功能应用程序中的状态"对象，并且收到此错误未捕获的TypeError:无法读取未定义的属性"状态".代码是

I am trying to get 'state' object in function Application which is out from General class and I am getting this error "Uncaught TypeError: Cannot read property 'state' of undefined". The code is

class General extends Comment {
  constructor() {
    super();
    this.state = { comments: first_comment};
  }
}

const Application = () => {
  return (
    <div> Hello world beginner: {this.state.comments}</div>
  );
};

render(<Application/>, document.getElementById('container'));

推荐答案

应用程序是无状态组件.更不用说箭头函数具有上下文的词汇范围.

Application is stateless component. Not to say that arrow functions have lexical scoping of context.

将道具用于无状态组件.

Use props for stateless components.

const Application = (props) => {
  return (
    <div> Hello world beginner: {props.comments}</div>
  );
};

或扩展React.Component

Or extend React.Component

class Application extends React.Component {
  constructor() {
     // init state
  }

  render() {
    return <div> Hello world beginner: {this.state.comments}</div>
  }
}

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