获取处于redux状态的未定义对象

const initialState = {
  user: null, // 或者 { name: '', email: '' }
};

function rootReducer(state = initialState, action) {
  switch (action.type) {
    case 'SET_USER':
      return { ...state, user: action.payload };
    default:
      return state;
  }
}

const user = useSelector(state => state.user);
console.log(user?.name); // 安全访问user对象的name属性

const user = useSelector(state => state.user);
if (user) {
  console.log(user.name);
} else {
  console.log('User is not defined');
}

const initialState = {
  loading: false,
  user: null,
  error: null,
};

function userReducer(state = initialState, action) {
  switch (action.type) {
    case 'FETCH_USER_REQUEST':
      return { ...state, loading: true };
    case 'FETCH_USER_SUCCESS':
      return { ...state, loading: false, user: action.payload };
    case 'FETCH_USER_FAILURE':
      return { ...state, loading: false, error: action.payload };
    default:
      return state;
  }
}

const { loading, user, error } = useSelector(state => state.user);

if (loading) return <div>Loading...</div>;
if (error) return <div>Error: {error.message}</div>;

return user ? <UserDetails user={user} /> : <div>No user data available</div>;