Update firebase value based on existing value

Hi , After the update i started having problem updating a value from firebase based on the already exisitng value. so let’s take for example the case of quantity of a specific product.

before i was able to do that :

let item$ = this.af.object('/product/' + productId) item$.take(1).subscribe( item=> { if(item.$exist()) item$.update({ quantity : item.quantity + 1}) })

now with the new API i am having trouble getting that item and updating it in 1 command. Am i missing something ? Hope its not a stupid question but really having all in 1 command solves the issue of having to store locally a “quantity” ( 2 commands : getQuantity and updateQuantity )

Thanks,

Chaker

[Damasy]

this my code and it works good, but the problem is that product in set method is undefined! @alberthoekstra

const item$ = this.db.object('/shopping-carts/' + cartId + '/items/' + product.key);
item$.snapshotChanges().pipe(take(1)).subscribe(item => {
  if (item.payload.exists()) {
      item$.update({ quantity: item.payload.val().quantity + 1 });
    } else {
      item$.set({product: product, quantity: 1});
    }
});

[vijaya1407]

There is still one error showing i.e. Property ‘quantity’ doesn’t exist on ‘{}’ . To resolve this, you have to change item.payload.val().quantity to item.payload.exportVal().quantity. const item$ = this.getItem(cartId, product.key);

item$.snapshotChanges().pipe(take(1)).subscribe(item => {
  if (item.payload.exists()) {
    item$.update({
      quantity: item.payload.exportVal().quantity + 1
    });
  } else {
    item$.update({product: product, quantity: 1});
  }
});