等待action更新react-native和redux中的状态

Question

我有一个简单的react-native应用程序和一个redux存储设置.基本上我想添加一个新故事,发送redux动作并在创建后转换到这个新故事.

我的Container Component中有以下代码,当用户点击add按钮时会运行该代码.

 addStory() {
    this.props.actions.stories.createStory()
      .then(() => Actions.editor({ storyId: last(this.props.stories).id }); // makes the transition)
  }

以及动作创作者.

export const createStory = () => (dispatch) => {
  dispatch({ type: CREATE_STORY, payload: { storyId: uniqueId('new') } });
  return Promise.resolve();
};

如您所见,我在动作创建者中返回一个承诺.如果我不在此处返回承诺,则将在状态更新之前进行转换.

这对我来说有点奇怪 - 为什么我必须在这里返回一个已经解决的Promise？不是发送意味着同步吗？

Answer 1

如评论中所述

回调示例:

addStory() {
    this.props.actions.stories.createStory( (id) => {
        Actions.editor({ storyId: id })
    });
}
export const createStory = ( callback ) => (dispatch) => {
    const _unique_id = uniqueId('new');
    dispatch({ type: CREATE_STORY, payload: { storyId: _unique_id } });
    callback(_unique_id);
};

超时示例: 这里我们假设状态现在已经更新了......大多数情况并非如此.

addStory() {
    this.props.actions.stories.createStory()
    setTimeout( () => {
        Actions.editor({ storyId: last(this.props.stories).id });
    }, 500);
}
export const createStory = () => (dispatch) => {
    dispatch({ type: CREATE_STORY, payload: { storyId: uniqueId('new') } });
};

承诺: 这可能需要一秒或一分钟才能完成..没关系.你做了你必须在这里做的一切,并最终解决它,以便应用程序/组件可以执行下一步操作.

export const createStory = () => (dispatch) => {
    return new Promise( (resolve, reject) => {
        // make an api call here to save data in server
        // then, if it was successful do this
        dispatch({ type: CREATE_STORY, payload: { storyId: uniqueId('new') } });
        // then do something else
        // do another thing
        // lets do that thing as well
        // and this takes around a minute, you could and should show a loading indicator while all this is going on
        // and finally
        if ( successful ) {
            resolve(); // we're done so call resolve.
        } else {
            reject(); // failed.
        }
    });
};

现在,结帐http://reactivex.io/rxjs/