TypeError: Cannot set property for while execution of passed the function

Question

I'm new to functional programming. While passing function to another function in type script, I'm getting error. Here is my code: -

export class NavigationComponent implements OnInit {

  constructor(public globals: Globals, public auth: AuthService, public placeService: PlaceService) {
    auth.handleAuthentication();
    if (auth.isAuthenticated) {
      console.log(' userName ' + this.firstName + ' userName ' + this.userName + ' dp ' + this.dpUrl);
      this.fetchProfile();
      console.log(' userName ' + this.firstName + ' userName ' + this.userName + ' dp ' + this.dpUrl);
    }
  }

  ngOnInit() {
    this.getCountries();
  }

  private firstName: any;
  private userName: any;
  private dpUrl: any;

  private fetchProfile() {
    this.auth.getProfileReponse(this.processResponse);
  }

  public processResponse(userResponse: Observable<HttpResponse<UserResp>>) {
    userResponse.subscribe(resp => {
      const user: User = { ...resp.body }.flatUser;
      console.log('user');
      console.log(user); // printing user perfetcly
      console.log(user.firstName); // printing user perfetcly
      this.firstName = user.firstName; // facing error here
      this.userName = user.userName;
      this.dpUrl = user.dpURL;
      // console.log(this.flatUser);
    });
  }
}

Error is as below:-

core.js:2090 ERROR TypeError: Cannot set property 'firstName' of undefined
at SafeSubscriber.eval [as _next] (navigation.component.ts:83)
at SafeSubscriber.__tryOrUnsub (Subscriber.js:240)
at SafeSubscriber.next (Subscriber.js:187)
at Subscriber._next (Subscriber.js:128)

why this 'firstName' of undefined, I'm using angular 6 beta version. Please help me to resolve this issue.

Possible duplicate of How to access the correct `this` inside a callback? — Estus Flask
– Estus Flask, Commented May 5, 2018 at 19:11

user184994 · Accepted Answer · 2018-05-05 18:38:55Z

1

It's actually the context of this that is undefined. Try this instead:

this.auth.getProfileReponse(() => this.processResponse);

The arrow syntax will bind to this, and it should prevent the error

answered May 5, 2018 at 18:38

user184994

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1 Comment

Raj Bhatia Over a year ago

it worked baba, you are beautiful. Thank you so much.

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