Encountering a navCtrl problem in Ionic 3 while attempting to utilize it within a service

I am currently working on a feature to automatically route users to the Login Page when their token expires. However, I am encountering an issue with red lines appearing under certain parts of my code.

  return next.handle(_req).do((event: HttpEvent<any>) => {

The problematic lines are here:

this.navCtrl.push('LoginPage');

Below is the full snippet of the code in question:

import { switchMap } from 'rxjs/operators';
import { TokenProvider } from './token/token';
import { Observable } from 'rxjs/Observable';
import { fromPromise } from 'rxjs/observable/fromPromise';
import { Injectable } from '@angular/core';
import {
  HttpInterceptor,
  HttpRequest,
  HttpHandler,
  HttpEvent,
  HttpResponse,
  HttpErrorResponse
} from '@angular/common/http';
import {
  IonicPage,
  NavController,
  NavParams,
  AlertController,
  LoadingController
} from 'ionic-angular';


@Injectable()
export class TokenInterceptor implements HttpInterceptor {
  constructor(private tokenProvider: TokenProvider) {}

  intercept(
    req: HttpRequest<any>,
    next: HttpHandler
  ): Observable<HttpEvent<any>> {
    return fromPromise(this.tokenProvider.GetToken()).pipe(
      switchMap(token => {
        const headersConfig = {
          'Content-Type': 'application/json',
          Accept: 'application/json'
        };
        if (token) {
          headersConfig['Authorization'] = `beader ${token}`;
        }
        const _req = req.clone({ setHeaders: headersConfig });
        return next.handle(_req).do((event: HttpEvent<any>) => {
      if (event instanceof HttpResponse) {
        // do stuff with response if you want
      }
    }, (err: any) => {
      if (err instanceof HttpErrorResponse) {
        if (err.status === 401) {
          this.navCtrl.push('LoginPage');
          // or show a modal
        }
      }
    });
      })
    );
  }
}

In order to resolve these issues and ensure smooth navigation to the Login Page upon token expiration, what changes should be made to the code?

Answer №1

To correctly use this.navCtrl, you must first import the NavController. You can find more information on how to do this at the following link: (https://ionicframework.com/docs/v3/api/navigation/NavController/)

import { NavController } from 'ionic-angular';

class MyComponent {
  constructor(public navCtrl: NavController) {

  }
  service(){
    this.navCtrl.push('MyPage');
  }
}

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