“Error-ReferenceError-ErrorEvent is not defined” for NativeScript app

问题

I am a new learner of NativeScript. I am following a video tutorial on Coursera to create an Android project using NativeScript, and I got the above error that is made by this part of my code:

process-httpmsg.service.ts :

import { Injectable } from '@angular/core';

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

@Injectable({
  providedIn: 'root'
})
export class ProcessHTTPMsgService {

  constructor() { }

  public handleError(error: HttpErrorResponse | any) {
    let errMsg: string;

    if (error.error instanceof ErrorEvent) {
      errMsg = error.error.message;
    } else {
      errMsg = `${error.status} - ${error.statusText || ''} ${error.message}`;
    }

    return throwError(errMsg);
  }
}

dish.services.ts:

import { Injectable } from '@angular/core';
import { Dish } from '../shared/dish';

import { Observable } from 'rxjs';
import { map, catchError } from 'rxjs/operators';
import { HttpClient, HttpHeaders } from '@angular/common/http';
import { baseURL } from '../shared/baseurl';
import { ProcessHTTPMsgService } from './process-httpmsg.service';

@Injectable({
  providedIn: 'root'
})
export class DishService {

  constructor(private http: HttpClient,
    private processHTTPMsgService: ProcessHTTPMsgService) { }

  getDishes(): Observable<Dish[]> {
    return this.http.get<Dish[]>(baseURL + 'dishes')
      .pipe(catchError(this.processHTTPMsgService.handleError));
  }

  getDish(id: string): Observable<Dish> {
    return this.http.get<Dish>(baseURL + 'dishes/' + id)
      .pipe(catchError(this.processHTTPMsgService.handleError));
  }

  getFeaturedDish(): Observable<Dish> {
    return this.http.get<Dish[]>(baseURL + 'dishes?featured=true').pipe(map(dishes => dishes[0]))
      .pipe(catchError(this.processHTTPMsgService.handleError));
  }
}

menu.component.html:

<ActionBar title="Menu" class="action-bar">
</ActionBar>
<StackLayout class="page">
    <ListView [items]="dishes" class="list-group" *ngIf="dishes">
        <ng-template let-dish="item">
            <StackLayout orientation="horizontal" class="list-group-item">
                <Image row="0" col="0" rowSpan="2" height="108" width="108"  [src]="BaseURL + dish.image" class="thumb p-16"></Image>
                <GridLayout class="list-group-item" rows="auto *" columns="*">
                    <Label row="0" col="0" [text]="dish.name" class="list-group-item-heading"></Label>
                    <Label row="1" col="0" class="list-group-item-text" [text]="dish.description"></Label>   
                </GridLayout>
            </StackLayout>
        </ng-template>
    </ListView>
    <ActivityIndicator busy="true"  *ngIf="!(dishes || errMess)" width="50" height="50" class="activity-indicator"></ActivityIndicator>
    <Label *ngIf="errMess" [text]="'Error: ' + errMess"></Label>
</StackLayout>

menu.component.ts:

import { Component, OnInit, Inject } from '@angular/core';
import { Dish } from '../shared/dish';
import { DishService } from '../services/dish.service';


@Component({
  selector: 'app-menu',
  moduleId: module.id,
  templateUrl: './menu.component.html',
  styleUrls: ['./menu.component.css']
})
export class MenuComponent implements OnInit {

  dishes: Dish[];
  errMess: string;

  constructor(private dishService: DishService,
    @Inject('baseURL') private baseURL) { }

  ngOnInit() {
    this.dishService.getDishes()
      .subscribe(dishes => this.dishes = dishes,
        errmess => this.errMess = <any>errmess);
  }

}

I don't know which other parts of the project's code is needed to put, so let me know that please.

EDIT: baseURL.ts:

// export const baseURL = "http://localhost:3000/";

export const baseURL = "http://192.168.1.5:3000/";

回答1:

As I already mentioned you can not do error.error instanceof ErrorEvent as ErrorEvent is an interface not class. You could do error.error instanceof HttpErrorResponse.

You can not hit http://localhost:3000 from your Simulator / Emulator, you are suppose to hit your api by your machine's IP as they are in same network but technically different (simulated) devices.

来源：https://stackoverflow.com/questions/56577315/error-referenceerror-errorevent-is-not-defined-for-nativescript-app