freeCodeCamp/common/app/routes/Jobs/redux/fetch-jobs-saga.js

import { Observable } from 'rx';
import { normalize, Schema, arrayOf } from 'normalizr';

import { fetchJobsCompleted } from './actions';
import { fetchJobs } from './types';
import { handleError } from '../../../redux/types';

const job = new Schema('job', { idAttribute: 'id' });

export default function fetchJobsSaga(action$, getState, { services }) {
  return action$
    .filter(action => action.type === fetchJobs)
    .flatMap(action => {
      const { payload: id } = action;
      const data = { service: 'jobs' };
      if (id) {
        data.params = { id };
      }
      return services.readService$(data)
        .map(jobs => {
          if (!Array.isArray(jobs)) {
            jobs = [jobs];
          }
          const { entities, result } = normalize(
            { jobs },
            { jobs: arrayOf(job) }
          );
          return fetchJobsCompleted(
            entities,
            result.jobs[0],
            result.jobs
          );
        })
        .catch(error => Observable.just({ type: handleError, error }));
    });
}