patterns-2-cancel-parallel-requests.js

import { race, cancel, take, fork, all, put, select } from 'redux-saga/effects';

export function* fetchDataForPage() {
  const userId = yield select(getUserId);

  try {
    if (!userId) {
      throw new Error('No user - aborting');
    }

    const apiCalls = yield all([
      fork(requestAndPut, [requestData, 'current', userId, MAX_CURRENT], requestOneActionCreator),
      fork(requestAndPut, [requestData, 'past', userId, MAX_PAST], requestTwoActionCreator)
    ]);

    const { cancelSagas, success } = yield race({
      cancelSagas: take(ON_PAGE_CHANGED),
      success: waitForTheseRequestsToFinish()
    });

    // If cancelSagas wins the race, cancel all of our sagas
    if (cancelSagas) {
      for (let i = 0; i < apiCalls.length; i++) {
        yield cancel(apiCalls[i]);
      }
    }
    else {
      return success;
    }
  }
  catch (e) {
    yield put({ type: ON_PAGE_MOUNT_ERROR, payload: e });
  }
}

// Returns true when all of these action types are fired
function* waitForTixRequestsToFinish() {
  yield all([
    take(ON_REQUEST_ONE_SUCCESS),
    take(ON_REQUEST_TWO_SUCCESS)
  ]);

  return true;
}