同时执行多个任务

import { call } from 'redux-saga/effects'

// effects 将会同步执行
const [users, repos] = yield [
  call(fetch, '/users'),
  call(fetch, '/repos')
]

saga中的超时处理

import { race, call, put } from 'redux-saga/effects'
import { delay } from 'redux-saga'

function* fetchPostsWithTimeout() {
  const {posts, timeout} = yield race({
    posts: call(fetchApi, '/posts'),
    timeout: call(delay, 1000)
  })

  if (posts)
    put({type: 'POSTS_RECEIVED', posts})
  else
    put({type: 'TIMEOUT_ERROR'})
}

race 的另一个有用的功能是，它会自动取消那些失败的 Effects。

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

function* backgroundTask() {
  while (true) { ... }
}

function* watchStartBackgroundTask() {
  while (true) {
    yield take('START_BACKGROUND_TASK')
    yield race({
      task: call(backgroundTask),
      cancel: take('CANCEL_TASK')
    })
  }
}