访问从异步调用返回的数组项目的问题

Question

我正在我的操作中的异步调用中返回一个数组，然后将其传递到还原器，最后回到react中。但是，每当我尝试访问内部元素时，我都会出现错误。我的第一个猜测是我的异步电话是错误的，所以我到处都是console.log。但是，除了我尝试映射数组时，一切似乎都很好。

这是一系列步骤：

Dispatch Action:

.then(feeds => {
            console.log('Sending data to dispatch');
            console.log(`Testing this function -> ${JSON.stringify(feeds)}`);
            dispatch({
                type: 'RETRIEVE_FEEDS',
                payload: feeds,
            });

最初feeds是我的还原器中的一个空数组，然后用此数组填充。

Reducer:

 case 'RETRIEVE_FEEDS': {
            return { ...state, feeds: action.payload };
        }

现在，在我的mapStateToProps中，我收到初始的空数组，然后收到来自调度的填充数组。

const mapStateToProps = ({ feedState }) => {
    const { feeds } = feedState;
    console.log(`FeedState -> ${JSON.stringify(feedState.feeds)}`);
    console.log(`Is Array -> ${Array.isArray(feedState.feeds)}`);
    console.log(`Going to map through the array`);
    feedState.feeds.map(feed =>{
        console.log(`Feed -> ${JSON.stringify(feed)}`)
        console.log(`Feed ID -> ${feed.feedID}`)
    });
    return { feeds };
};

我唯一的问题是，每当我尝试从数组中获取东西时，它都会变得不确定。

这些是我的日志：

FeedState -> []
Is Array -> true
Going to map through the array
Sending data to dispatch
Testing this function -> [[{"feedID":"57dfnQuwUghupbRB7EEB","uploadedBy":"8Vmr0ZnVDPfgkCqSBWHXjaVEDYH3","videoURL":"","datePosted":"2017-12-08T14:24:37.323Z","tags":[],"isLike":false,"likes":{"countLikes":0}}],[{"feedID":"reYEcurssCV32WyQgOYp","uploadedBy":"8Vmr0ZnVDPfgkCqSBWHXjaVEDYH3","videoURL":"","datePosted":"2017-12-08T14:46:13.655Z","tags":[],"isLike":false,"likes":{"countLikes":0}}]]
FeedState -> [[{"feedID":"57dfnQuwUghupbRB7EEB","uploadedBy":"8Vmr0ZnVDPfgkCqSBWHXjaVEDYH3","videoURL":"","datePosted":"2017-12-08T14:24:37.323Z","tags":[],"isLike":false,"likes":{"countLikes":0}}],[{"feedID":"reYEcurssCV32WyQgOYp","uploadedBy":"8Vmr0ZnVDPfgkCqSBWHXjaVEDYH3","videoURL":"","datePosted":"2017-12-08T14:46:13.655Z","tags":[],"isLike":false,"likes":{"countLikes":0}}]]
Is Array -> true
Going to map through the array
Feed -> [{"feedID":"57dfnQuwUghupbRB7EEB","uploadedBy":"8Vmr0ZnVDPfgkCqSBWHXjaVEDYH3","videoURL":"","datePosted":"2017-12-08T14:24:37.323Z","tags":[],"isLike":false,"likes":{"countLikes":0}}]

Feed ID -> undefined

Answer 1

看起来，从您的日志中，feedState.feeds中的每个项目都是一个数组。因此feed.feedID无法正常工作。 feed[0].feedID会起作用。

您的.map功能也应返回某些内容，您应该使用映射的数组来做某事。即feeds.map的结果