Angular2 rxjs - switchmap 捕获错误

# 使用Angular 2中的RxJS SwitchMap捕获错误

typescript
import { Component } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable, throwError } from 'rxjs';
import { catchError, switchMap } from 'rxjs/operators';
@Component({
  selector: 'app-root',
  template: `
    
      Fetch Data
      
{{ data }}
      
{{ error }}
    
  `,
})
export class AppComponent {
  data: string;
  error: string;
  constructor(private http: HttpClient) {}
  getData() {
    this.http.get('https://jsonplaceholder.typicode.com/posts/1')
      .pipe(
        switchMap((result: any) => {
          // Simulate an error
          if (result.id === 1) {
            return throwError('Error fetching data!');
          }
          return new Observable((observer) => {
            observer.next(result.title);
            observer.complete();
          });
        }),
        catchError((err) => {
          this.error = err;
          return throwError(err);
        })
      )
      .subscribe((result) => {
        this.data = result;
      });
  }
}