用于嵌套mergeMap调用的Angular 6 api

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable } from 'rxjs';
import { mergeMap } from 'rxjs/operators';

@Injectable({
  providedIn: 'root'
})
export class ApiService {
  constructor(private http: HttpClient) {}

  fetchUser(userId: string): Observable<any> {
    return this.http.get(`https://api.example.com/users/${userId}`);
  }

  fetchPosts(userId: string): Observable<any> {
    return this.http.get(`https://api.example.com/posts?userId=${userId}`);
  }

  fetchUserWithPosts(userId: string): Observable<any> {
    return this.fetchUser(userId).pipe(
      mergeMap(user => {
        return this.fetchPosts(user.id).pipe(
          mergeMap(posts => {
            return { user, posts };
          })
        );
      })
    );
  }
}

import { catchError } from 'rxjs/operators';
import { of } from 'rxjs';

fetchUserWithPosts(userId: string): Observable<any> {
  return this.fetchUser(userId).pipe(
    mergeMap(user => {
      return this.fetchPosts(user.id).pipe(
        mergeMap(posts => {
          return { user, posts };
        }),
        catchError(error => {
          console.error('Error fetching posts:', error);
          return of({ user, posts: [] }); // 返回一个默认值或空数组
        })
      );
    }),
    catchError(error => {
      console.error('Error fetching user:', error);
      return of(null); // 返回null或其他默认值
    })
  );
}