Question

我有一个GET请求，如果我将创建者作为api / watchlist /？creator = 5dac9d3567aca81e40bfc0之类的参数添加到帖子中，然后在Postman中对其进行测试，结果将正确返回该创建者的所有帖子以及以下代码。 / p>

app.js

  app.get('/api/watchlist',(req, res, next)=>{
  Watching.find({ creator: req.query.creator})
  .then(documents => {
    console.log("Creator value: " + req.query.creator);
   res.status(200).json({
     message: 'User\'s watchlist items retrieved!',
     posts: documents

  });

   });
   });

如果我尝试将GET请求拉入angular，那么它什么也不会返回。当我打开相关网页时，前端也说前端在说ERROR TypeError: "retrievedData.posts is undefined" getWatchListItems watch-list.service.ts:72

watch-list.service.ts

getWatchListItems（创建者：字符串）{

this.http
  .get<{ message: string; posts: any; maxPosts: number; watchlist: string }>(
    "http://localhost:3000/api/watchlist?creator=" + creator
  )
  .pipe(
    map(retrievedData  => {
      console.log(retrievedData.watchlist);
               return {
        posts: retrievedData.posts.map(post => {
      console.log(retrievedData.watchlist);
          return {
        title: post.title,
        cost: post.cost,
        listingOwner: post.listingOwner,
        id: post._id
          };

        }),
        maxPosts: retrievedData .maxPosts
      };
    })
  )
  .subscribe(transformedPostData => {
    console.log(transformedPostData);
    this.posts = transformedPostData.posts;
    this.postsUpdated.next({
      listing: [...this.posts],
      postCount: transformedPostData.maxPosts
    });
  });

}

watching.component.ts

 ngOnInit() {
    this.userId = localStorage.getItem("userId: ");
    //  this.userId = this.authService.getUserId();
    this.watchListService.getWatchListItems(this.userId);
    this.postsSub = this.watchListService
      .getPostUpdateListener()
      .subscribe((postData: { listing: Watching[]; postCount: number }) => {

        this.totalPosts = postData.postCount;
        this.posts = postData.listing;

      });

  }

Answer 1

您将在角服务中将创建作为路径参数发送。

因此，您需要像这样修改api：

app.get('/api/watchlist/:creater', (req, res, next) => {
  Watching.find({ creator: req.params.creator })
    .then(documents => {
      console.log("Creator value: ", req.params.creator);
      res.status(200).json({
        message: 'User\'s watchlist items retrieved!',
        watchlist: documents
      });
    });
});

如果您不想更改api，则应将创建者作为查询参数发送，如下所示：

return this.http
      .get<{ message: string; posts: any; maxPosts: number }>(
        "http://localhost:3000/api/watchlist?creator=" + creator
      )

此后，您必须按角度处理响应数据，并转换为您的需求。

您可以通过在console.log结果中包含此代码来更新问题吗？（据我所知，您不需要订阅该服务，就是在订阅您的组件）

getWatchListItems(creator: string) {

  return this.http("http://localhost:3000/api/watchlist?creator=" + creator)
    .pipe(
      map(retrievedData => {
        console.log("retrievedData: ", retrievedData);
        //todo: transform retrievedData

        return retrievedData;
      })
    )
}

别忘了您的api以这种格式返回数据，因此您应该

{
  "watchlist": ...
   "message": ...
}

GET请求在Postman的后端工作，但向前端返回null

1 个答案: