javascript - React Hook "useSelector"在函数中被调用

Question

我无法弄清楚“useSelector”发生了什么，我需要一点帮助。

错误

React Hook "useSelector" is called in function "render_user" which is neither a React function component or a custom React Hook function

class Navigationbar extends Component {

  onLogoutClick = e => {
    e.preventDefault();
    this.props.logoutUser(); //this.props.
  };

  render() {
      const render_user = () => {

        const auth = useSelector(state => state.auth); Error Message is here
        //More Code Here
      );
    };
  } 

Navigationbar.propTypes = {
  logoutUser: PropTypes.func.isRequired,
  auth: PropTypes.object.isRequired
};

const mapStateToProps = state => ({
  auth: state.auth
});

export default connect(
  mapStateToProps,
  { logoutUser }
)(Navigationbar);

Answer 1

错误是因为您违反了 rules of hooks :

• Only Call Hooks at the Top Level
• Only Call Hooks from React Functions

违规行为:

1. useSelector() 未在顶层调用。它在 render() 中的 render_user() 中调用(即嵌套函数)。
2. useSelector() 是类组件的一部分，Navigationbar

你可以提取一个组件来遵循钩子(Hook)的规则并使用useSelector:

function User() { // Rule 2: call hooks in function component
  const auth = useSelector(state => state.auth); // Rule 1: call hooks in top-level
  return <>{auth}</>
}

class Navigationbar extends Component {

  render_user() {
    if (props.authenticated) {
      return <User />
    }
    // not yet authenticated
    // do something else
  }

  render() {
    return <>{this.render_user()}</>
  }
}