如何使用 Angular 8 NgRx 函数方法发送另一个有效的动作？

Question

My develop environment does not indicate a problem (full green), but an error occurs when I run it. (I will get http404 and cacheError will run. It is fine now like "error test".)

Error message: ERROR TypeError: "You provided '() => ({ type })' where a stream was expected. You can provide an Observable, Promise, Array, or Iterable. I see but I would like to dispatch loginFailed a action without props.

HttpIntercept is exist! So url will be http://localhost:PORT/user/login . Just it is not available.

actions.ts

// imports

export const types = {
    loginStart: '[User] Login start',
    loginSuccess: '[User] Login success',
    loginFailed: '[User] Login fail',
};

export const loginStart = createAction(types.loginStart, props<ILogin>());
export const loginSuccess = createAction(types.loginSuccess, props<IUser>());
export const loginFailed = createAction(types.loginFailed);

effect.ts

import { types } from './actions';
import * as fromActions from './actions';
// and more imports

@Injectable()
export class UserEffects {
    constructor(
        private actions$: Actions,
        private http: HttpClient,
        private router: Router,
    ) {
    }

    loginProcess = createEffect(() => this.actions$.pipe(
        ofType(types.loginStart),
        exhaustMap((action) => {
            return this.http.post<IUser>('/user/login', {
                username: action.username,
                password: action.password,
            }).pipe(
                map(data => {
                    console.log(data);
                    return fromActions.loginSuccess(data);
                }),
                catchError((err) => { // this will run
                    console.log(err);
                    return fromActions.loginFailed;
                }),
            );
        })
    ));
}

Answer 1

catchError expects you to return an observable so perhaps try something like this using of :

catchError((err) => { // this will run
    console.log(err);
    return of(fromActions.loginFailed());
}),

Answer 2

It's odd that you're not getting a error at compile time, but I think it might be because the RxJS catchError operator expects an observable to be returned.

Something like =>

catchError(err =>
  of(featureActions.LoadFailureAction({ err }))
),

Ran into this issue a while back and found this article from Wes Grimes (Google Developer Expert in Angular and NgRx core team member) to be really helpful. https://itnext.io/ngrx-best-practices-for-enterprise-angular-applications-6f00bcdf36d7