[redux] Create sagas to handle resolve/reject actions

[diegohaz]

Currently we are handling resolve/reject on every saga. To reduce the boilerplate, it should be handled by a separated saga, like I did here: https://github.com/tramaLabs/web/blob/39f5b8b31e39d5d604e04ad60cbdf046bc1c6859/src/store/status/sagas.js

import { fork, take } from 'redux-saga/effects'

export function* watchResolveReject () {
  const resolvers = {}
  const rejecters = {}
  while (true) {
    const { type, resolve, reject, ...rest } = yield take('*')
    let [ suffix, ...prefix ] = type.split('_').reverse()
    prefix = prefix.reverse().join('_')
    yield { prefix, suffix }

    switch (suffix) {
    case 'REQUEST':
      resolvers[prefix] = resolve
      rejecters[prefix] = reject
      break
    case 'SUCCESS':
      if (resolvers[prefix]) {
        resolvers[prefix](rest)
        delete resolvers[prefix]
      }
      break
    case 'FAILURE':
      if (rejecters[prefix]) {
        rejecters[prefix](rest)
        delete rejecters[prefix]
      }
    }

    yield { resolvers, rejecters }
  }
}

export default function* () {
  yield fork(watchResolveReject)
}

[diegohaz]

This snippet runs split(), reverse(), reverse() and join() for every action dispatched on the store (take('*')). I'm not sure how this affects performance though.

const { type, resolve, reject, ...rest } = yield take('*')
let [ suffix, ...prefix ] = type.split('_').reverse()
prefix = prefix.reverse().join('_')
// given SOME_ACTION_REQUEST, prefix = SOME_ACTION, suffix = REQUEST

Just to illustrate how wonderful generators are:

function* generator () {
  const number = yield 'foo'
  const sum = 2 + number
  yield sum
}

const gen = generator()

function* generator () {
  const number = yield 'foo'
                           ^ starts here
  const sum = 2 + number
  yield sum
}

expect(gen.next().value).toEqual('foo')

function* generator () {
  const number = yield 'foo'
                 ^---------- pauses here and returns 'foo'
  const sum = 2 + number
  yield sum
}

expect(gen.next(4).value).toEqual(6)

function* generator () {
  const number = yield 'foo'
        ^------------------- passes back 4 to number
  const sum = 2 + number
  yield sum
  ^------------------------- runs until it finds another yield, then returns the value (6)
}