Can't assing null to next value for reply subject

Issue

I'm new to angular and I'm trying to assign null value for replysubject in angular . I exactly wrote my code from tutorial but i wonder why i cant assign null value for this kind of object. Here's my code from my service class.

import { HttpClient } from '@angular/common/http';
import { Injectable } from '@angular/core';
import { ReplaySubject } from 'rxjs';
import {map} from 'rxjs/operators';
import { User } from '../_models/user';
@Injectable({
  providedIn: 'root'
})
export class AccountService {
  baseUrl="https://localhost:5001/api/";
  private currentUserSource=new ReplaySubject<User>(1);
  currentUser$=this.currentUserSource.asObservable();

  constructor(private http:HttpClient) {

   }

  login(model: any) {
    return this.http.post<User>(this.baseUrl + 'account/login', model).pipe(
      map((response: User) => {
        const user = response;
        if (user) {
         localStorage.setItem('user',JSON.stringify(user));
         this.currentUserSource.next(user);
        }
      })
    )
  }

  setCurrentUser(user:User){
    this.currentUserSource.next(user);
  }

  logout(){
    localStorage.removeItem('user');
    ****this.currentUserSource.next(null);****   this line won't compile
  }
}

Solution

1. The map operator must return something. If not it might return undefined to the subscribers. You're better off using the tap operator here seeing there are no response transformations required.

login(model: any): Observable<User> {
  return this.http.post<User>(this.baseUrl + 'account/login', model).pipe(
    tap((response: User) => {
      const user = response;
      if (user) {
        localStorage.setItem('user',JSON.stringify(user));
        this.currentUserSource.next(user);
      }
    })
  );
}

2. About the error, most probably the tutorial was written pre-Angular Ivy. With Ivy AoT enabled, the values pushed must conform to the types defined. In your case you're pushing null to observable of type User. You could either disable Ivy or use union types to also accept null.

private currentUserSource=new ReplaySubject<User | null>(1);

Answered By - ruth