为什么在应用程序组件中进行服务注入会导致URL参数未定义？

Question

I have a service where I read couple of parameters from the URL. looks good till I try to inject the service in the constructor of the app.component.ts or I try to call a service method from the app.component.ts . Then the url-parameters are undefined.

Any idea what could be the reason for that?

my-service.service.ts :

...
public param1;
constructor(public router: Router, private http: HttpClient) {
    this.param1 = 
     this.router.parseUrl(this.router.url).queryParams['todo'];
    console.log('param1: ' + this.param1); // returns undefined if the service is injected in app.component
}
....

app.component.ts :

...
import { MyService } from './service/my-service.service';
....
constructor(private http: HttpClient, public myService: MyService) {
    ...
}

Answer 1

When we pass some params we always do it this way:

import { Router, ActivatedRoute } from '@angular/router';

  constructor(
    private router: Router,
    private route: ActivatedRoute
  ){ 
      this.route.params.subscribe(params => {
        let todo = params['todo'];
      });
  }

Maybe you have to move the subscription to ngOnInit() but normally this should work.