CODEWITHSUNDEEP
javascriptangularrxjs
Walter White
Walter White

Reputation: 1024

next() don't notify subscribe()

I have some service 

isDocAdd: Subject<boolean> = new Subject<boolean>();

addDocument(header) {
        return this.http.post(this.addHl7DocumentUrl, header)
            .map((response: any) => { if (response.status === '404') {
                    this.isDocAdd.next(true);
                }
                else {
                    this.isDocAdd.next(false);
                }
                return response;
            })
            .catch((error: Error) => {
                console.error('Error:', error);
                return Promise.reject(error.message || error);
            });
    }

and In component.ts subscribe() notification

subscription: Subscription;
message;

constructor(private documentService: DocumentService) {
    this.subscription = this.documentService.isDocAdd.subscribe(val => { this.message = val; });

}

In method addDocument() this.isDocAdd.next(val) is set but don't notify component about changes and subscribe() method does not execute.

Upvotes: 0

Views: 83

Answers (3)

user4676340
user4676340

Reputation:

This is because your component is created after your service.

This means, your subject is not known by your component, so you call next while nothing has subscribed.

One solution is to use a BehaviorSubject instead : 

isDocAdd: BehaviorSubject<boolean> = new BehaviorSubject<boolean>();

It works exactly the same, but a BehaviorSubject will notify its observers when you instanciate them (even if the value is null, so test that !)

Upvotes: 2

Borad Akash
Borad Akash

Reputation: 804

private isDocAdd= new Subject<boolean>();
isDocAdd$ = this.isDocAdd.asObservable();
addDocument(header) {
        return this.http.post(this.addHl7DocumentUrl, header)
            .map((response: any) => { response.status === '404') {
                    this.isDocAdd.next(true);
                }
                else {
                    this.isDocAdd.next(false);
                }
                return response;
            })
            .catch((error: Error) => {
                console.error('Error:', error);
                return Promise.reject(error.message || error);
            });
    }

and in component.ts

subscription: Subscription;
message;

constructor(private documentService: DocumentService) {
    this.subscription = this.documentService.isDocAdd$.subscribe(val => { this.message = val; });
}

Upvotes: 1

Sachila Ranawaka
Sachila Ranawaka

Reputation: 41445

Need to create an observable from your subject in order to subscribe to it. use asObservable

isDocAdd: Subject<boolean> = new Subject<boolean>();
onChanged: Observable<boolean> = this.isDocAdd.asObservable();

Now subscribe to the onChanged 

this.subscription = this.documentService.onChanged.subscribe(val => { this.message = val; });

Upvotes: 0

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