Use select effect in normal function/eventChannels

Question

I am using redux sagas event channel. I have a specific use case where i want to getStore state when event gets triggered as eventChannel is not generator function i am not able to use select effect of redux sagas. Any other way to achieve this ?

I had also tried to import store and use store.getState() but i am getting undefined as saga file is imported before store gets initialized.

function subscribe(socket) {
    return eventChannel(emit => {
        socket.subscribe(listenerTopic, {qos: 1});
        socket.on('reconnection', () => {
            // i need to fetch latest unread message, for that i need to get timestamp
           // for last message received which is in store so the command will be to 
         // send sinceDate i.e last message timestamp and untilDate that is currentDate
   })
}

Answer 1

One possible solution would be to use redux-saga channel feature. The idea would be to push an event into the channel each time a socket event occurs. At the same time you have another saga listening for events on the channel and reacts accordingly. Because the listening part is a saga, you can use common saga effects like select.

Your code could probably look like this:

import { channel } from 'redux-saga'
import { select } from 'redux-saga/effects'

const socketChannel = channel()

function subscribe(socket) {
  return eventChannel(emit => {
     socket.on('reconnection', () => {
       socketChannel.put({ type: RECONNECTION })
     })
  })
}

export function* watchSocketChannel() {
  while (true) {
    const action = yield take(socketChannel)

    if (action.type === RECONNECTION) {
      const lastMessageTimestamp = yield select(selectors.getLastMessageTimestamp)
      ...
    }
  }
}

I hope this will help you.