I have a service with a theme: @Injectable() export class UserService() { private currentU...">
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Filter out all "null" values ​​from observable <T>

I have a service with a theme:

@Injectable() export class UserService() {
    private currentUserSubject = new BehaviorSubject<User>(null);
    public currentUser = this.currentUserSubject.asObservable().distinctUntilChanged(); 

    ... // emitting new User    
}

Have a component that I insert this service and subscribe to updates:

@Component() export class UserComponent {
    constructor(private userService: UserService) {
        this.userService.currentUser
            .subscribe((user) => {
                // I want to see not null value here
            })
    }
}

I want to apply something to Observable<User>

in order to filter out all null values ​​and only enter the subscription on download User

.

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2 answers


Add a filter operator to your observable chain. You can filter the zeros explicitly, or just check that your user is truthful - you will have to make this call depending on your needs.

Filtering only null users:



public currentUser = this.currentUserSubject
                         .asObservable()
                         .filter(user => user !== null)
                         .distinctUntilChanged();
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There is a way to check the existing value



public currentUser = this.currentUserSubject
                         .asObservable()
                         .filter(Boolean)
                         .distinctUntilChanged();
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