SimpleReducer_ErrorReducer.js

SimpleReducer_ErrorReducer.js

// api/errorReducer.js
export const errorReducer = (state = {}, action) => {
  const { type, payload } = action;
  const matches = /(.*)_(REQUEST|FAILURE)/.exec(type);

  // not a *_REQUEST / *_FAILURE actions, so we ignore them
  if (!matches) return state;

  const [, requestName, requestState] = matches;
  return {
    ...state,
    // Store errorMessage
    // e.g. stores errorMessage when receiving GET_TODOS_FAILURE
    //      else clear errorMessage when receiving GET_TODOS_REQUEST
    [requestName]: requestState === 'FAILURE' ? payload.message : '',
  };
};

// api/selectors.js
import _ from 'lodash';
export const createErrorMessageSelector = (actions) => (state) => {
  // returns the first error messages for actions
  // * We assume when any request fails on a page that
  //   requires multiple API calls, we shows the first error
  return _(actions)
    .map((action) => _.get(state, `api.error.${action}`))
    .compact()
    .first() || '';
};