Redux-Saga卡在收益通知上

Question

I try to run the next code on node 6.2.1. It logs 1, 2, and then stuck. I cannot undestand why it doesn't continue execution to the line yield take('TEST')... Seems that anotherSaga finishes and logs 2 but control isn't returned to rootSaga. Can anyone help me please?

const {runSaga, delay} = require('redux-saga');
const {take, put, call} = require('redux-saga/effects');

function* anotherSaga() {
  yield call(delay, 1000);
  console.log(2);
}

function* rootSaga() {
  while(true) {
    console.log(1);
    yield call(anotherSaga);
    console.log(3);
    const action = yield take('TEST');
    console.log(4);
    yield put(action);
  }
}

runSaga(
  rootSaga(),
  {
    subscribe(callback) {
      return setInterval(() => (callback({type: 'TEST'})), 1000);
    },
    dispatch(action) {
      console.log(action);
    },
    getState() {}
  }
);

Update : but code without runSaga works as expected logging 1,2,3,4

const {createStore, applyMiddleware} = require('redux');
const createSagaMiddleware = require('redux-saga').default;
const {delay} = require('redux-saga');
const {take, put, call} = require('redux-saga/effects');

function* anotherSaga() {
  yield call(delay, 2000);
  console.log(2);
}

function* rootSaga() {
  while(true) {
    console.log(1);
    yield call(anotherSaga);
    console.log(3);
    const action = yield take('TEST');
    console.log(4);
    yield put(action);
    console.log('---')
  }
}

const rootReducer = (state, action) => {
  if (state === undefined) {
    return {};
  }

  return state;
}

const sagaMiddleware = createSagaMiddleware();
const store = createStore(rootReducer, {}, applyMiddleware(sagaMiddleware));
sagaMiddleware.run(rootSaga);

setInterval(() => (store.dispatch({type: 'TEST'})), 1000);

Answer 1

It looks like this is due to the subscribe function not returning the correct value. Above it's returning the result of setInterval , which will be the ID of the interval. Instead it should be returning a function that redux-saga can use to unsubscribe to events, as per the docs . So your subscribe function should look more like this:

subscribe(callback) {
  const intervalId = setInterval(() => (callback({type: 'TEST'})), 1000);
  return () => { clearInterval(intervalId); };
},

Running it with this, I was able to see it loop through printing

1
2
3
4
{ type: 'TEST' }

It's weird how this caused your saga to become stuck, but I'm assuming that not receiving an unsubscribe function from subscribe caused things to become messed up internally in redux-saga.