訪問 object 中的數組長度給我“TypeError：無法讀取未定義的屬性“長度”

Question

我收到一個錯誤TypeError: Cannot read property 'length' of undefined當試圖訪問我從 mapstatetoprops 獲得的 object 中的數組長度時...成功返回 object。 in my component i call this.props.getuserdata in componentdidMount, and i mapstatetoprops currentUser state with getUserdata... although tt returns an object, it does not allow me to access the length of one of the properties arrays.... my mapstatetoprops寫道：

當前用戶：state.currentUser.getUserData

組件文件夾

    class Users extends Component {

  componentDidMount() {
    this.props.getUserData();
    this.props.getOtherUsers();
   }

  render() {
      console.log(this.props.currentUser.myStocks.length,'current user')
      
      return (
      <Container>
      
      </Container>
    )
  }
};
function mapStateToProps(state) {
  return {
   currentUser: state.currentUser.getUserData, 
    filteredUsers: state.filteredUsers.getOtherUsers,
    getUsersError: state.users.getUsersError
  };
}

export default compose(
  connect(mapStateToProps, { getUserData, getOtherUsers }),
  requireAuth
)(Users);

動作文件夾：

    export const getUserData = () => async (dispatch) => {
   try {
    const { data } = await axios.get('/api/user/profile', {
      headers: { authorization: localStorage.getItem('token') },
    });
    // console.log(data.myStocks[0],'inform')
    dispatch({ type: GET_USER_DATA, payload: data });
  } catch (e) {
    dispatch({
      type: GET_USER_DATA_ERROR,
      serverError: e,
      clientError: 'Something went wrong please refresh try again',
    });
  }
}

Answer 1

如果this.props.currentUser應該通過this.props.getUserData()獲得，則問題可能是您的 API 調用未完成，而反應使用render方法。