private customer: Subject<Object> = new BehaviorSubject<Object>(null);
setCustomer(id, accountClassCode) {
this.customer.next({'id': id, 'accountClassCode': accountClassCode});
}
getCustomer() {
return this.customer.asObservable();
}
I'm using this part of code but I'm getting an error that can not find id of null. Is there any solution to get initial value that is not null?
The purpose of BehaviorSubject is to provide initial value. It can be null or anything else. If no valid initial value can be provided (when user id isn't known yet), it shouldn't be used.
ReplaySubject(1) provides a similar behaviour (emits last value on subscription) but doesn't have initial value until it is set with next.
It likely should be
private customer: Subject<Object> = new ReplaySubject<Object>(1);
new ReplaySubject<Foo>() is better. Specifying the type does nothing at runtime btw, but provides type safety at compile time. –
Mccullough ReplaySubject.create<Object>(1) –
Oas map(([one, two]) => ({ one, two })) –
Arezzo Data out? –
Insectivorous BehaviorSubject where updating for every same value. I made a Set extension method that checks the current value. Also I believe I need current value in other places –
Insectivorous value property, exactly because it always has a value. Other subjects and observables don't. In case you want to be able to always get current value from other kinds of subjects, you need to extend them and expose it in the same way that BehaviorSubject does, github.com/ReactiveX/rxjs/blob/master/src/internal/… –
Arezzo Since the object can be null, a better choice is to infer the type like this
private customer = new BehaviorSubject<Customer|null>(null);
Try structuring this way your service:
Service:
@Injectable()
export class MyService {
customerUpdate$: Observable<any>;
private customerUpdateSubject = new Subject<any>();
constructor() {
this.customerUpdate$ = this.customerUpdateSubject.asObservable();
}
updatedCustomer(dataAsParams) {
this.customerUpdateSubject.next(dataAsParams);
}
}
Remember to add MyService to providers.
Where you update your client (if this is the case), you do something like this:
Component (The one that triggers):
constructor(private myService: MyService) {
// I'll put this here, it could go anywhere in the component actually
// We make things happen, Client has been updated
// We store client's data in an object
this.updatedClient = this.myObjectWithUpdatedClientData; // Obj or whatever you want to pass as a parameter
this.myService.updatedCustomer(this.updatedClient);
}
Component (The one that is Subscribed):
this.myService.customerUpdate$.subscribe((updatedClientData) => {
// Wow! I received the updated client's data
// Do stuff with this data!
}
);
From what I understood, you are trying to pass data from 1 component to another. You get your Client's data and send it over your App to another component, right? That's why I posted this solution.
If you are interested in other types of subscriptions, read this:
Angular 2 special Observables (Subject / Behaviour subject / ReplaySubject)
Another way is to use pipe to filter until a non-null value is received. It can be done with takeWhile also.
.pipe(filter(val => !!val)).subscribe(x => {});
pipe(skipWhile(val => !!val)) –
Poleax I have found many cases where I want the simplicity of ReplaySubject(1) but also want the value property of BehaviorSubject, i.e. it stores your most recent value for retrieval without having to subscribe. And using BehaviorSubject was always annoying given the need for an initial value that gets broadcast, a condition I rarely wanted. To that end I created my own CurrentSubject.
import { ReplaySubject } from "rxjs";
export class CurrentSubject<T> extends ReplaySubject<T> {
value: T;
set(value?: T) {
this.value = value;
this.next(value);
}
}
I wanted to override the next method but I couldn't get that to work for some reason, so I settled on a method called set. My override attempt looked like this...
export class CurrentSubject<T> extends ReplaySubject<T> {
value: T;
next(value?: T) {
this.value = value;
super.next(value);
}
}
I don't know why overriding didn't work.
next is called on the extension class, nextInfiniteTimeWindow is actually executed by ReplaySubject, but when overriding next and calling super.next, it's next from the Subject class that get called instead of nextInfiniteTimeWindow. I didn't bother fixing the problem so I instead wrapped the ReplaySubject class in my own class and exposed the same methods. –
Wadmal next method with the latest versions of TypeScript & RxJS. Any idea? –
Eldin you can initialize empty
final xpto = BehaviorSubject<List< XPTO >>.seeded([]);
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new BehaviorSubject<Object>({});instead? – Veteran