如何在 Redux 中处理两个连续和依赖的 Async 调用? [英] How to handle two consecutive and dependent Async calls in Redux?

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问题描述

我通过从 componentDidMount 上的组件调用操作 fetchPosts 异步获取帖子列表.我想,一旦该请求被相关的减速器(它更新状态)接收并处理,就调用另一个动作 fetchPostsMetaData,并使用刚刚接收到的帖子的 id 数组.

I am getting a list of posts asynchronously by calling an action fetchPosts from a Component on componentDidMount. I would like, once that request is received and handled by the relevant reducer (which updates the state), to call another action fetchPostsMetaData, with an array of the just-received posts' ids.

我正在使用 redux-thunk 中间件,并使用 jQuery.ajax

I am using redux-thunk middleware, and making my ajax requests using jQuery.ajax

解决这个问题的最佳方法是什么?我试过谷歌搜索,但找不到相关的例子/答案.

What is the best way to go about this? I tried googling but couldn't find a relevant example / answer.

推荐答案

使用redux-thunk:

class PostIndex extends React.Component {
  componentDidMount() {
    const { dispatch } = this.props;
    dispatch(getPosts());
  }
  ...
}

function fetchPosts() {
  return dispatch => {
    fetchPostsAjax()
      .then(res => {
        dispatch({ type: 'RECEIVE_POSTS', payload: res });
        dispatch(fetchPostMeta(res));
      })
  }
}

function fetchPostMeta(posts) {
  return dispatch => {
    fetchPostMetaAjax(posts)
      .then(res => dispatch({ type: 'RECEIVE_POST_META', payload: res }));
    }
  }
}

function fetchPostAjax() {
   // return a promise, whether from jQuery.ajax or fetch
}

function fetchPostMetaAjax() {
  // return a promise
}

这是 redux-thunk 的一个非常标准的用例.上面的示例迎合了您提出问题的方式,但您可以在一个看起来像此处提供的 redux-thunk 示例的单个动作创建器中完成此操作:http://redux.js.org/docs/advanced/AsyncActions.html

This is a pretty standard use-case for redux-thunk. The above example is catered towards the way you're asking the question, but you could accomplish this in a single action creator that looks the the redux-thunk example provided here: http://redux.js.org/docs/advanced/AsyncActions.html

不同的是,在我的示例中,我在 thunk 内部调度 thunk,而不是直接在第一个 thunk 内部执行第二个任务.所以它相当于:

Whats different is that in my example, I'm dispatching a thunk inside of a thunk, rather than doing the second task directly inside of the first thunk. So its equivalent to this:

function fetchPosts() {
  return dispatch => {
    fetchPostsAsync()
      .then(res => { // res is posts
        dispatch({ type: 'RECEIVE_POSTS', payload: res });
        return fetchPostMetaAsync(res);
      })
      .then(res => { // res  is metadata
        dispatch({ type: 'RECEIVE_POST_META', payload: res });
      })
  }
}

您不会遇到任何竞争条件,因为当您调度像 { type: RECEIVE_POSTS, payload: res } 这样的操作时,它是同步的,并且在您调度以下异步操作之前,reducer 会更新.

You won't run into any race conditions because when you dispatch an action like { type: RECEIVE_POSTS, payload: res }, it is synchronous and the reducer updates before you dispatch the following async action.

这篇关于如何在 Redux 中处理两个连续和依赖的 Async 调用?的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!

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