Ionic 4- Receive variable update with Behaviorsubject

Question

In the home I have a list of products that click opens the product modal with a button to add to cart. When you add the quantity appears next to the icon. I want to close this modal on app. be updated the icone that is in the footer. I need to update this cart with the value of the modal that was closed without refresh.

service.ts

 public totalShop: BehaviorSubject<String>;

 constructor() {
    this.totalShop = new BehaviorSubject('0');       
 }

 setTotalShop(val) {    
    this.totalShop.next(val);    
  }

  clearTotalShop() {
    this.totalShop.next('0');
  }

  getTotalShop(){    
    return this.totalShop.asObservable();
  }

modalProduct.ts

 fnShop(){
    quantidade = quantidade +1
    this.servico.setTotalShop(quantidade)
 }

app.componentts.

 quantshop;
 subscription: Subscription;

 ngOnInit(): void {
   this.subscription = this.servicol.getTotalShop().subscribe(val => this.quantshop = val);
   console.log(this.quantshop)
}

app module.

  providers: [servico]

image