如何从initialState中选择特定值？React - Redux

const initialState = {
  counter: 0,
  user: {
    name: 'John',
    age: 25
  }
};

const selectUserName = state => state.user.name;

import { useSelector } from 'react-redux';

const MyComponent = () => {
  const userName = useSelector(selectUserName);

  return (
    <div>
      <p>User Name: {userName}</p>
    </div>
  );
};

import { connect } from 'react-redux';

class MyComponent extends React.Component {
  render() {
    const { userName } = this.props;

    return (
      <div>
        <p>User Name: {userName}</p>
      </div>
    );
  }
}

const mapStateToProps = state => ({
  userName: selectUserName(state)
});

export default connect(mapStateToProps)(MyComponent);