Redux-saga get data from action returns patternOrC

问题:

I need to send dynamic data from my screen to action/reducer and fetch data from API with that data, but when i yield in my rootSaga i'll get an error like this:

uncaught at check take(patternOrChannel): patternOrChannel is undefined
uncaught at rootSaga at rootSaga
at takeEvery
Error: take(patternOrChannel): patternOrChannel is undefined

Screen code:

import { checkUserLoginStatus, userSignin } from '../actions/user';

class PreCheckout extends PureComponent {
   handleLogin = () => {
     this.props.dispatch(userSignin(username, password));
   };
   render() { .......

Action:

const USER_SIGNIN = 'USER_SIGNIN';

export const userSignin = (username, password) => ({
   type: USER_SIGNIN,
   username,
   password,
});

Reducer:

import {
  CHECK_USER_LOGIN_STATUS,
  USER_SIGNIN,
  USER_SIGNIN_RESULT,
  USER_SIGNIN_ERROR,
} from '../actions/user';

const initialState = {
  isLoggedIn: false,
  isFetching: false,
  information: {},
  error: null,
};

const reducer = (state = initialState, action) => {
  switch (action.type) {
    case CHECK_USER_LOGIN_STATUS:
      return {
        ...state,
      };
    case USER_SIGNIN:
      return {
        ...state,
        isFetching: true,
      };
    case USER_SIGNIN_RESULT:
      return {
        ...state,
        isFetching: false,
        information: action.result,
      };
    case USER_SIGNIN_ERROR:
      return {
        ...state,
        isFetching: false,
        error: action.error,
      };

Redux-Saga:

import {
  USER_SIGNIN,
  USER_SIGNIN_RESULT,
  USER_SIGNIN_ERROR,
} from '../actions/user';

function* fetchUserInformation(action) {
  try {
    console.log('fetchUserInformation action: ', action);
    const response = yield call(login, action);
    yield put({
      type: USER_SIGNIN_RESULT,
      result: response.result,
    });
  } catch (e) {
    yield put({
      type: USER_SIGNIN_ERROR,
      error: e.message,
    });
  }
}

export default function* rootSaga() {
  yield takeEvery(USER_SIGNIN, fetchUserInformation);
}

回答1:

As I have mention in comment. You simply forgot to export the constant.

Should be

export const USER_SIGNIN = 'USER_SIGNIN';

Or

const USER_SIGNIN = 'USER_SIGNIN';

...

export { USER_SIGNIN };

These types of bugs could be captured by eslint using eslint-plugin-import with this rule enabled.

回答2:

Probably USER_SIGNIN is undefined.