使用一个调用 observable 的函数，其中 3 个不同的 observable 与 switch map 绑定在一起。结果出错

Question

我有一个函数，当文件上传到 html 表单时运行。

uploadidnexttofacepicture(event){
    let subscription = this.s3service.publicresourceuploadtos3(event)
      .subscribe((req: any)=>{
        console.log(req);
      });
    
  }

此函数从注入的服务调用函数 publicresourceuploadtos3。此函数显示如下：

publicresourceuploadtos3(event): Observable<any>{
    console.log('the service at least ran');

    const mediatobeuploaded = event.target.files[0];
    this.http.get(environment.public_generate_presigned_url_resource).pipe(
      switchMap((req : any)=>{
        console.log('did the call to the server');

        const resourceurl = req.uriroot + req.fields.key;

        let fd = new FormData();
        fd.append('acl', req.fields.acl);
        fd.append('key', req.fields.key);
        fd.append('content-type', req.fields['content-type']);
        fd.append('policy', req.fields.policy);
        fd.append('x-amz-algorithm', req.fields['x-amz-algorithm']);
        fd.append('x-amz-credential', req.fields['x-amz-credential']);
        fd.append('x-amz-date', req.fields['x-amz-date']);
        fd.append('x-amz-signature', req.fields['x-amz-signature']);
        fd.append('file', mediatobeuploaded);
        this.http.post(req.url, fd).pipe(
          switchMap((req2: any)=>{
            const result = {
              resourceurl : resourceurl,
              resourcekey: req.fields.key
            };
            return of(result);


        }));


      }));


  }

控制台日志 console.log('the service at least ran'); 确实在控制台中触发，但服务器调用了一个：console.log('did the call to the server'); 没有。

但这会导致错误：

ERROR TypeError: Cannot read property 'subscribe' of undefined
    at ContentcreatorverificationComponent.uploadidnexttofacepicture

我担心这是一个语法问题，如果你们知道发生了什么，将会有所帮助。

Answer 1

尝试在this.http.get(environment.public_generate_presigned_url_resource)

之前添加return

应该是这样的

 publicresourceuploadtos3(event): Observable<any>{
    console.log('the service at least ran');

    const mediatobeuploaded = event.target.files[0];
   return this.http.get(environment.public_generate_presigned_url_resource).pipe(
      switchMap((req : any)=>{
        console.log('did the call to the server');

        const resourceurl = req.uriroot + req.fields.key;

        let fd = new FormData();
        fd.append('acl', req.fields.acl);
        fd.append('key', req.fields.key);
        fd.append('content-type', req.fields['content-type']);
        fd.append('policy', req.fields.policy);
        fd.append('x-amz-algorithm', req.fields['x-amz-algorithm']);
        fd.append('x-amz-credential', req.fields['x-amz-credential']);
        fd.append('x-amz-date', req.fields['x-amz-date']);
        fd.append('x-amz-signature', req.fields['x-amz-signature']);
        fd.append('file', mediatobeuploaded);
        this.http.post(req.url, fd).pipe(
          switchMap((req2: any)=>{
            const result = {
              resourceurl : resourceurl,
              resourcekey: req.fields.key
            };
            return of(result);


        }));


      }));


  }

使用一个调用 observable 的函数，其中 3 个不同的 observable 与 switch map 绑定在一起。结果出错

using a function that calls observable with 3 different observables tied together with switch map. results in error

angular

typescript

rxjs

rxjs-observables

switchmap