类型“只读<{}>"上不存在属性“值" [英] Property &#39;value&#39; does not exist on type &#39;Readonly&lt;{}&gt;&#39;

问题描述

我需要创建一个表单，该表单将根据 API 的返回值显示一些内容.我正在使用以下代码:

I need to create a form that will display something based on the return value of an API. I'm working with the following code:

class App extends React.Component {
  constructor(props) {
    super(props);
    this.state = {value: ''};

    this.handleChange = this.handleChange.bind(this);
    this.handleSubmit = this.handleSubmit.bind(this);
  }

  handleChange(event) {
    this.setState({value: event.target.value});
  }

  handleSubmit(event) {
    alert('A name was submitted: ' + this.state.value); //error here
    event.preventDefault();
  }

  render() {
    return (
      <form onSubmit={this.handleSubmit}>
        <label>
          Name:
          <input type="text" value={this.state.value} onChange={this.handleChange} /> // error here
        </label>
        <input type="submit" value="Submit" />
      </form>
    );
  }
}

我收到以下错误:

error TS2339: Property 'value' does not exist on type 'Readonly<{}>'.

我在代码注释的两行中遇到了这个错误.这段代码甚至不是我的，我是从 react 官方网站 (https://reactjs.org/docs/forms.html)，但它在这里不起作用.

I got this error in the two lines I commented on the code. This code isn't even mine, I got it from the react official site (https://reactjs.org/docs/forms.html), but it isn't working here.

我正在使用 create-react-app 工具.

Im using the create-react-app tool.

推荐答案

Component 定义如下:

interface Component<P = {}, S = {}> extends ComponentLifecycle<P, S> { }

表示状态(和道具)的默认类型是:{}.
如果你想让你的组件在 state 中有 value 那么你需要像这样定义它:

Meaning that the default type for the state (and props) is: {}.
If you want your component to have value in the state then you need to define it like this:

class App extends React.Component<{}, { value: string }> {
    ...
}

或者:

type MyProps = { ... };
type MyState = { value: string };
class App extends React.Component<MyProps, MyState> {
    ...
}

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