如何循环史诗般的通话

Question

我有以下史诗：

import {
  map,
  catchError,
  switchMap,
  takeUntil,
} from 'rxjs/operators';
import {
  FETCH_JOKES,
  jokesReceived,
  FETCH_JOKES_CANCELLED,
  jokesFetchFailed,
} from '../actions/jokes-action';
import { ofType } from 'redux-observable';
import { of, concat } from 'rxjs';
import { ajax } from 'rxjs/ajax';

const getJokes = () =>
  ajax.getJSON('http://api.icndb.com/jokes/random?escape=javascript');

const fetchJokesEpic = action$ => {
  return action$.pipe(
    ofType(FETCH_JOKES),
    switchMap(() =>
      getJokes().pipe(
        map(response => jokesReceived(response)),
        catchError((err, act) => of(jokesFetchFailed(err))),
        takeUntil(action$.pipe(ofType(FETCH_JOKES_CANCELLED)))
      )
    ),
  );
};

export default fetchJokesEpic;

每当FETCH_JOKES 被调度时，这个史诗就会开始ajax 调用，成功调度jokesReceived 操作或失败jokesFetchFailed。

我想循环它，所以除非取消，否则端点将在上次调用完成（成功或失败）后再次调用。

我想我可以使用另一个史诗般的 taht 对 JOKES_RECEIVED 和 FETCH_JOKES_ERROR 动作做出反应，然后调度 FETCH_JOKES 动作应该再次开始 cricle。

import { ofType } from 'redux-observable';
import {
  delay,
  map,
} from 'rxjs/operators';
import {
  JOKES_RECEIVED,
  FETCH_JOKES_CANCELLED,
  FETCH_JOKES_ERROR,
  fetchJokes,
} from '../actions/jokes-action';

const pollJokes = (action$, state$) => {
  return action$.pipe(
    ofType(JOKES_RECEIVED, FETCH_JOKES_ERROR, FETCH_JOKES_CANCELLED),
    delay(2000),
    map(action => {
      console.log('pollJokes.map', action);
      if(action.type === FETCH_JOKES_CANCELLED)
      { 
        console.log("Cancelled")
        return { type: 'POLL_STOPPED' };
      }
      else {
        // loop
        return fetchJokes();
      }
    })
  );
};
export default pollJokes;

但是，当我发送 FETCH_JOKES_CANCELLED 操作时，这不起作用。操作堆栈如下所示：

@INIT
FETCH_JOKES
JOKES_RECEIVED
FETCH_JOKES
JOKES_RECEIVED
...
FETCH_JOKES_CANCELLED
FETCH_JOKES
JOKES_RECEIVED
POLL_STOPPED
FETCH_JOKES
JOKES_RECEIVED
...

我尝试将 takeUntil 添加到 pollJokes 史诗中，但结果同样糟糕

const pollJokes = (action$, state$) => {
  return action$.pipe(
    ofType(JOKES_RECEIVED, FETCH_JOKES_ERROR, FETCH_JOKES_CANCELLED),
    delay(2000),
    map(action => {
      console.log('pollJokes.map', action);
      if(action.type === FETCH_JOKES_CANCELLED)
      { 
        console.log("Cancelled")
        return { type: 'POLL_STOPPED' };
      }
      else {
        // loop
        return fetchJokes();
      }
    }),


    takeUntil(action$.pipe(ofType(FETCH_JOKES_CANCELLED)))


  );
};

使用这种方法，pollJokes 史诗在FETCH_JOKES_CANCELLED 首次发送后立即停止工作。现在我知道史诗在takeUntil 完成。

我该怎么做才能让这种“循环”工作？我猜想实现一个中间件，当JOKES_RECEIVED 调度时，它实际上会调用fetchJokes，但我正在寻找一个全rxjs 解决方案，

Answer 1

你需要使用repeat，为了重新启动你的史诗，一旦它被takeUntil取消了

const pollJokes = (action$, state$) => {
  return action$.pipe(
    ofType(JOKES_RECEIVED, FETCH_JOKES_ERROR, FETCH_JOKES_CANCELLED),
    delay(2000),
    map(action => {
      console.log('pollJokes.map', action);
      if(action.type === FETCH_JOKES_CANCELLED)
      { 
        console.log("Cancelled")
        return { type: 'POLL_STOPPED' };
      }
      else {
        // loop
        return fetchJokes();
      }
    }),


    takeUntil(action$.pipe(ofType(FETCH_JOKES_CANCELLED))),
    repeat()

  );
};