使用Redux获取帖子的作者和承诺的顺序
使用Redux获取帖子的作者和承诺的顺序
提问于 2018-10-14 19:12:13
使用React Native和Redux，我正在尝试首先获取一些帖子，然后获取相应的作者。
我面对两个问题：
- 如何调整
catch和then语句的顺序？我想说的是:如果无法获取帖子，则发送失败操作，停止，不做任何其他操作(即，不尝试获取作者)。但是，如果帖子被成功获取，请继续获取作者。 - 我需要在下面的代码中进行哪些更改，以确保将
posts传递给fetchAuthorsForPostsFromAPI？按原样，fetchAuthorsForPostsFromAPI.
中的posts是undefined
// fetches the posts from the API
export const fetchPostsFromAPI = () => ( dispatch ) => {
// dispatch action: currently fetching posts from the API
dispatch( fetchingPosts() );
// prepare the promise that fetches the posts from the API
let loadPosts = new Promise( ( resolve, reject ) => {
// uses dummy data for now
if( !postsInitial ) {
reject( "Error: Could not get posts" );
}
else {
resolve( postsInitial );
}
});
// actually fetch the posts from the API
return loadPosts
// if error fetching the posts from the API
.catch( error => dispatch( fetchPostsFailure( error ) ) )
// if success fetching the posts from the API
.then( posts => dispatch( fetchPostsSuccess( posts ) ) )
// fetch authors for posts from the API
.then( posts => fetchAuthorsForPostsFromAPI( posts, dispatch ) )
}// is dispatched if the posts were succesfully fetched from the API
function fetchPostsSuccess( posts ) {
return {
type: PostConstants.FETCH_POSTS_SUCCESS,
postsWithoutAuthors: posts,
}
}// is called when the posts have been fetched successfully from the API
// fetches the author for each post from the API
function fetchAuthorsForPostsFromAPI( posts, dispatch ) {
console.log( "posts:", posts ); // logs "posts: undefined"
// dispatch action: currently fetching authors of posts from the API
dispatch( fetchingAuthorsForPosts() );
// prepare the promise that fetches the authors for the posts from the API
let loadAuthors = new Promise( ( resolve, reject ) => {
// for each post
posts.map( post => {
// find the author by id
const authorObj = authors.find( author => {
return author.id === post.authorId
});
// if error finding author
if( !authorObj ) {
reject( "Error: Author for this id could not be found!" );
}
// if success finding author, keep going
else {
post.author = authorObj;
}
});
// resolve
resolve( posts );
});
// actually fetch the authors from the API
return loadAuthors
// if success fetching the authors for the posts from the API
.then( posts => dispatch( fetchPostsAuthorsSuccess( posts ) ) )
// if error fetching the authors for the posts from the API
.catch( error => dispatch( fetchPostsAuthorsFailure( error ) ) );
}回答 1
Stack Overflow用户
发布于 2018-10-15 01:35:50
有几种方法可以解决这个问题。我使用async/await比promise简单得多。
async const fetchData = () => (dispatch) => {
var postResult = await getPosts(dispatch);
if (postResult) {
await getAuthors();
}
}
const getPosts = async () => (dispatch) => {
var apiResponse = await getPostsFromApi();
if(apiResponse)
{
//dispatch something
return true;
} else {
//dispatch error
return false;
}
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/52802040
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