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应该在Redux中间件中最后调用“next”吗?

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tl;dr: Within a Redux middleware function, is it okay to dispatch a new action after calling next to finish updating the store?

我正在使用Flutterbuilt-flutter-redux构建一个HackerNews读者,基于Brian Egan的TodoMVC example . 它使用HN的Firebase支持的API来提取数据:

https://github.com/HackerNews/API

我的行为现在看起来像这样:

ActionDispatcher<Null> fetchHackerNewsTopStories;
ActionDispatcher<List<int>> fetchHackerNewsTopStoriesSuccess;
ActionDispatcher<Null> fetchHackerNewsTopStoriesFailure;
ActionDispatcher<Null> fetchNextHackerNewsItem;
ActionDispatcher<HackerNewsItem> fetchHackerNewsItemSuccess;
ActionDispatcher<Null> fetchHackerNewsItemFailure;

有一个中间件可以监听 fetchHackerNewsTopStories 操作并启动对API的调用:

MiddlewareHandler<AppState, AppStateBuilder, AppActions, Null>
createFetchHackerNewsTopStories(HackerNewsRepository service) {
  return (MiddlewareApi<AppState, AppStateBuilder, AppActions> api,
      ActionHandler next, Action<Null> action) {
    service.fetchHackerNewsTopStories().then((ids) {
      return api.actions.fetchHackerNewsTopStoriesSuccess(ids);
    }).catchError(api.actions.fetchHackerNewsTopStoriesFailure);

    next(action);
  };
}

当它返回时,我用ID列表更新我的应用程序状态 .

在某些时候,我需要发出另一个动作, fetchNextHackerNewsItem . 有's another middleware function that will listen for that action and request the details for the the first story. When those details arrive, it' ll请求下一个故事,依此类推,直到所有内容都更新 .

我想知道的是我是否可以这样做:

// Invoked when REST call for the list of top story IDs completes.
MiddlewareHandler<AppState, AppStateBuilder, AppActions, List<int>>
createFetchHackerNewsTopStoriesSuccess() {
  return (MiddlewareApi<AppState, AppStateBuilder, AppActions> api,
      ActionHandler next, Action<List<int>> action) {
    next(action);
    api.actions.fetchNextHackerNewsItem(); // Is this cool?
  };
} 

// Initiates a request for a single story's details.
MiddlewareHandler<AppState, AppStateBuilder, AppActions, Null>
createFetchNextHackerNewsItem(HackerNewsRepository service) {
  return (MiddlewareApi<AppState, AppStateBuilder, AppActions> api,
      ActionHandler next, Action<Null> action) {
    int nextId = api.state.topStoryIds[api.state.loadedUpToIndex];
    service.fetchHackerNewsItem(nextId).then((item) {
      return api.actions.fetchHackerNewsItemSuccess(item);
    }).catchError(api.actions.fetchHackerNewsTopStoriesFailure);

    next(action);
  };
}

因为 createFetchNextHackerNewsItem 依赖于应用程序的状态( api.state.topStoryIds[api.state.loadedUpToIndex] ),所以我希望它在 next(action) 调用更新商店后运行 .

在调用 next 后调用Redux中间件中的新操作是否很酷,还是某种反模式?如果它是反模式,那么实现此流程的最佳方法是什么?

1 回答

  • 2

    是的,没关系 - 中间件在发送动作时可以做任何想要的事情 . 这包括修改/记录/延迟/交换/忽略原始操作,以及调度其他操作 .

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