BehaviorSubject firing twice

6
votes

Im using BehaviourSubject from RxJS:

private rights = new BehaviorSubject<Array<string>>([]);


updateRights(rights: Array<string>) {
  this.rights.next(rights);
}

getRights(): Observable<any> {
  return this.rights.asObservable();
}

I'm updating the rights in the root component and im subscribing to it in another component like:

 this.configService.getRights().subscribe(res => {
   console.log(res);
 })

This subscription is firing twice. Once when the data is empty and then again when the data is received.

I want the subscription to fire only once and get only the latest data. What should be done?

2
rxjsangular7

2 Answers

6
votes

BehaviourSubject emits the value on subscription by default, and it is intended design. If you do not want this behaviour, use Subject instead.

0
votes

Do it this way:

private currnetRightsSubject: BehaviorSubject<string[]>;
public currentRights: Observable<string[]>;

constructor() {
    this.currnetRightsSubject= new BehaviorSubject<string[]>(/*.......*/);
    this.currentRights= this.currnetRightsSubject.asObservable();
}

public get currentRightsValue(){
    return this.currnetRightsSubject.value;
}

updated

fill the BehaviorSubject like this:

this.currnetRightsSubject.next(someValue);