类型错误：您在需要流的地方提供了“未定义”。 你可以提供一个 Observable、Promise、Array 或 Iterable

Question

I have an issue with catching error in Ionic based with Angular.

I am on create() method trying to create new User and if username already exists, i retrieve response from backend but on my method error throws the named message in title. I have tried most of the similar answers but still stuck

any help

Config.ts

import {HttpErrorResponse} from '@angular/common/http';
import {Observable, throwError} from 'rxjs';

export default class Config {

  static handleError(error: HttpErrorResponse): Observable<any> {
    console.log('*****handleErrors*****');
    console.log(error); //TypeError: You provided 'undefined' where a stream was expected. You can provide an Observable, Promise, Array, or Iterable.
    console.log(error.message); //TypeError: You provided 'undefined' where a stream was expected. You can provide an Observable, Promise, Array, or Iterable.
    console.log(error.error.message);

    return throwError(
      error.error.message());
  }
}

account.service.ts

  create(account: Account): Observable<Account> {
    return this.httpClient
      .post<ResponseWrapper>(this.accountsUrl, JSON.stringify(account), this.httpOptions).pipe(
        map(rw => {
          return rw.data;
        }),
        catchError(
          this.handleError
        )
      );
  }

 handleError(error: Response | any) {
    return Config.handleError(error);
  }

account-detail.page.ts, I didnt want to spam to much code with toastService I have created, but toastService is working

this.accountService.create(this.selectedAccount).subscribe(
        res => {
          this.selectedAccount = res;
          const io = new InteractionObject('save', 'account', this.selectedAccount);
          this.accountDetailEvent.emit(io);
          this.interactionService.setSave(io);
          setTimeout(() => {

          }, 500);
          this.toastService.showSaveSuccessMsg();
        },
        error => { //TypeError: You provided 'undefined' where a stream was expected. You can provide an Observable, Promise, Array, or Iterable.
          this.errorMsg = error;
          if ('ACCOUNT_USERNAME_EXISTS' === this.errorMsg) {
            this.toastService.showSaveFailMsg('account_username_exists');
          }
        }
      );

Answer 1

If you find no account, your map won't be able to return an Account, and you will not get into to catch if the request is OK.

To fix it, you could add a check on the response and if no account is found then, you throw an exception