结合来自多个rxjs可观察量的结果

Question

I have an autocomplete input which, as the user types, fetches data from multiple endpoints, such as:

//service call to fetch data and return as single observable
getAutocompleteSuggestions() {
    const subs$ = [
        this.http.get(endpoint1),
        this.http.get(endpoint2),
        this.http.get(endpoint3)
    ];

    return Observable.forkJoin(...subs$);
}

Each of these endpoints returns data of the form:

{ data: [], status: xyz }

I would like to use switchmap as I want to only show results from the final call, and have tried the following:

   this.getAutocompleteSuggestions(query)
          .switchMap(res => {
             return res.data;
           })
          .subscribe((results: any) => {
            this.results = results;
          });

But the 'res' in the switchmap is an array, any idea how results can contain a single array containing the data from the response of any number of observables?

Answer 1

I don't fully understand what you want, but I think this is it:

$filter: Subject<string> = new Subject(); //I guess we have some value to filter by??

Push a value to the subject:

this.$filter.next(myNewValue);

In the constructor or init:

this.$filter
   .switchMap(filterValue => { //Get the values when filter changes
       subs$ = [
         this.http.get(endpoint1 + filterValue),
         this.http.get(endpoint2 + filterValue),
         this.http.get(endpoint3 + filterValue)
       ];

       return Observable.forkJoin(...subs$);
   })
   .map(results => { //now map you array which contains the results
      let finalResult = [];
      results.forEach(result => {
          finalResult = finalResult.concat(result.data)
      })
      return final;
   })
   .subscribe(); //Do with it what you want

The entire steam will be executed again when we put a new value into our subject. SwitchMap will cancel all ready requests if there are any.

Answer 2

I have used something similar to this, and worked well so far:

        let endpoint1 = this.http.get(endpoint1);
        let endpoint2 = this.http.get(endpoint2);
        let endpoint3 = this.http.get(endpoint3);

        forkJoin([endpoint1, endpoint2, endpoint3])
          .subscribe(
            results => {
              const endpoint1Result = results[0].map(data => data);
              const endpoint2Result = results[1].map(data => data);
              const endpoint3Result = results[2].map(data => data);

              this.results = [...endpoint1Result, ...endpoint2Result, ...endpoint3Result];
            },
            error => {
              console.error(error);
            }
          );

Obviously is a pretty simple example, you'll be able to handle better the results to suit your needs.