Behaviour subject initial value null?

Answer 1

Try structuring this way your service:

Service:

@Injectable()
export class MyService {
    customerUpdate$: Observable;

    private customerUpdateSubject = new Subject();

    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)