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Redux-Saga controllable long-polling loop
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| import { take, put, call, fork, cancel, cancelled } from 'redux-saga/effects' | |
| import {EVENT_POLLING_START, EVENT_POLLING_STOP} from "constants/eventPolls"; | |
| import {ClientEventType} from "constants/serverEvents"; | |
| function* handleEventA(serverEvent) { | |
| yield put({type : serverEvent.type, payload : {name : serverEvent.eventAData}}); | |
| } | |
| function* handleEventB(serverEvent) { | |
| yield put({type : serverEvent.type, payload : serverEvent.eventBData}); | |
| } | |
| function* handleEventC(serverEvent) { | |
| const {eventCData} = serverEvent; | |
| const {field1, field2} = eventCData; | |
| yield put({type : serverEvent.type, payload : {field1, field2}}); | |
| } | |
| function* defaultEventHandler(serverEvent) { | |
| console.log("Unhandled server event type: ", serverEvent.type); | |
| } | |
| const serverEventHandlers = { | |
| [ClientEventType.EventA] : handleEventA, | |
| [ClientEventType.EventB] : handleEventB, | |
| [ClientEventType.EventC] : handleEventC, | |
| } | |
| function* handleServerEvent(serverEvent) { | |
| const eventHandler = serverEventHandlers[serverEvent.type] || defaultEventHandler; | |
| return yield eventHandler(serverEvent); | |
| } | |
| function* pollForEventsLoop(serverRPC) { | |
| let lastCallSucceeded = true; | |
| try { | |
| while(true) { | |
| const serverEvents = yield call(serverRPC.pollForEvents, lastCallSucceeded); | |
| yield serverEvents.map(handleServerEvent); | |
| } | |
| } | |
| finally { | |
| if (yield cancelled()) { | |
| console.log("Event poll loop cancelled"); | |
| } | |
| console.log("Event poll loop ended"); | |
| } | |
| } | |
| export default function* pollForEventsDriver(serverAPI) { | |
| const {serverRPC} = serverAPI; | |
| while ( yield take(EVENT_POLLING_START) ) { | |
| // starts the task in the background | |
| const pollForEventsTask = yield fork(pollForEventsLoop, serverRPC); | |
| // wait for the user stop action | |
| yield take(EVENT_POLLING_STOP); | |
| // user clicked stop. cancel the background task | |
| // this will throw a SagaCancellationException into the forked bgSync task | |
| yield cancel(pollForEventsTask); | |
| } | |
| } |
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