订阅/可观察到的抛出错误-Angular2 +

Question

我试图从观察到的函数中抛出错误，以便可以访问订阅的err部分，但似乎无法理解该部分。

Answer 1

I'm not sure how to do it via the map way, but here is a different way:

import { Observable, of, throwError } from 'rxjs';

  ngOnInit() {
    this.getObs().subscribe(data => {
      console.log(data);
    }, err => {
      console.log(err);
    });
  }

  getObs() {    
    const observable = of(6);
    const isError = true;
    if (isError) {
      return throwError("Is an error!");
    }
    return observable;
  }

Working example: https://stackblitz.com/edit/angular-mqp4qv?file=src/app/app.component.ts

Answer 2

Couple ways I would handle this. Heres one way using _throw

// auth.ts
import { _throw } from 'rxjs/observable/throw';

login( username, password ) {

    const body = this.jsonifyData( username, password );

    return this.http.post<any>( this.apiBaseUrl + '/auth', body )
        .pipe(
        map( res => {
            if ( 'token' in res ) {
                return res.token;
            }
            // Unsuccessful login returns error
            return _throw( res ); // from import {_throw} from 'rxjs/observable/throw';
        } )

    );
}

The other would be to just catch the error in the login component

Answer 3

I think in your component's test spec you need to mock up your authService and the login procedure. This mock does not make http call, just throw an error via throwError(new Error('Either username or password were incorrect')) immediately if, say, password does not match some predefined value. Here is some example of how to test component-http service stuff, it is a bit outdated but still actual conceptually.