Swift code to Add item with quantity in Firebase Database - firebase

Question

Using Swift code 5.1 I have managed to update Firestore Database with items in current users basket but not able to add/update quantity. Currently if I wanted to add an item that already exist in the basket it simply adds another line but I wanted to just update quantity.
Can you advise me on how to create a function that adds quantity?
Here are the codes I have so far. Only relevant sections of code pasted.
Firestore DB function in my Helper file:
enum FCollectionReference: String {
case User
case Category
case Items
case Basket
case Orders
}
func FirebaseReference(_ collectionReference: FCollectionReference) -> CollectionReference {
return Firestore.firestore().collection(collectionReference.rawValue)
}
Here's the code in in my Basket Model file using
class Basket {
var id: String!
var ownerId: String!
var itemIds: [String]!
var delivery: Float!
var admin: Float!
var quantity: Int!
init() {
}
init(_dictionary: NSDictionary) {
id = _dictionary[kOBJECTID] as? String
ownerId = _dictionary[kOWNERID] as? String
itemIds = _dictionary[kITEMIDS] as? [String]
delivery = _dictionary[kDELIVERY] as? Float
admin = _dictionary[kADMIN] as? Float
quantity = _dictionary[kQUANTITY] as? Int
}
}
//MARK: Helper functions
func basketDictionaryFrom(_ basket: Basket) -> NSDictionary {
return NSDictionary(objects: [basket.id, basket.ownerId, basket.itemIds, basket.quantity], forKeys: [kOBJECTID as NSCopying, kOWNERID as NSCopying, kITEMIDS as NSCopying, kQUANTITY as NSCopying,kDELIVERY as NSCopying, kADMIN as NSCopying])
}
//MARK: - Update basket
func updateBasketInFirestore(_ basket: Basket, withValues: [String : Any], completion: #escaping (_ error: Error?) -> Void) {
FirebaseReference(.Basket).document(basket.id).updateData(withValues) { (error) in
completion(error)
Codes in Item View Control to add items to basket:
#objc func addToBasketButtonPressed() {
//check if user is logged in or show login view
if MUser.currentUser() != nil {
downloadBasketFromFirestore(MUser.currentId()) { (basket) in
if basket == nil {
self.createNewBasket()
}else {
basket?.itemIds.append(self.item.id)
self.updateBasket(basket: basket!, withValues: [kITEMIDS: basket!.itemIds])
}
}
} else {
showLoginView()
}
}
private func updateBasket(basket: Basket, withValues: [String : Any]) {
updateBasketInFirestore(basket, withValues: withValues) { (error) in
if error != nil {
self.hud.textLabel.text = "Error: \(error!.localizedDescription)"
self.hud.indicatorView = JGProgressHUDErrorIndicatorView()
self.hud.show(in: self.view)
self.hud.dismiss(afterDelay: 2.0)
print("error updating basket", error!.localizedDescription)
}else {
self.hud.textLabel.text = "Added to Basket"
self.hud.indicatorView = JGProgressHUDSuccessIndicatorView()
self.hud.show(in: self.view)
self.hud.dismiss(afterDelay: 2.0)
}
}
}
To clarify my request, what do I need to change/re-arrange in my coding so the Database Cloud Firestore is arranged in order shown in my attached screen shot. First screen shot showing current layout in the last column and I'm trying to change this to layout demonstrated in the second screen shot?

Answer 1

I think you are asking how to update the value in a field within a Firestore document. If not, let me know and I will update the answer.
Here's some code that updates the qty of an item in inventory. Pass in the qty to add as a + Int and then to subtract as a - Int. The structure looks like this
root
inventory
item_0
qty: 0
and the code to update the qty node is:
func incrementQty(deltaQty: Int) {
let docToUpdate = self.db.collection("inventory").document("item_0")
docToUpdate.updateData( [
"qty": FieldValue.increment( Int64(deltaQty) )
])
}
call it like this
self.incrementQty(deltaQty: 4) //adds 4 to the existing qty
previously, incrementing values had to be wrapped into a transaction to make it safe but the FieldValue makes it much easier.

Answer 2

I am adding another answer based on comments and question clarification. My other answer still stands as an answer but it's a different approach.
Arrays are inherently hard to work with in NoSQL databases as they are often treated as a single object. They have limited functionality opposed to collections, documents and fields, and can't directly be sorted or have items inserted. And querying is well, challenging. Firestore does a great job at providing better interoperability with arrays but there are still usually better options.
Instead of an array, I would change the structure to this:
Baskets (collection)
basket_number (document in the Baskets collection, like you have now)
items //a collection of items in the basket
item_0 //a document with the docID being the the item number
item_qty: //qty of the item
item_1
item_qty:
item_2
item_qty:
So the downside of .updateData is that if the field being updated doesn't exist, it doesn't create the field, it simply throws an error. So we need to test to see if the document exists first, if so, update with updateData, if not create the item with an initial quantity.
Here's the code that does it - note for simplicity I am ignoring the top level Basket and basket_number since you already know how to do that part and focused on the items collection and down.
func incrementQty(itemNumberToUpdate: String, deltaQty: Int) {
let docToUpdate = self.db.collection("items").document(itemNumberToUpdate)
docToUpdate.getDocument(completion: { documentSnapshot, error in
if let err = error {
print(err.localizedDescription)
return
}
if let _ = documentSnapshot?.data() {
print("item exists, update qty")
docToUpdate.updateData([
"item_qty": FieldValue.increment( Int64(deltaQty) )
], completion: { err in
if let err = err {
print("Error updating document: \(err.localizedDescription)")
} else {
print("Item qty successfully updated")
}
})
} else {
print("no item exists, need to create")
docToUpdate.setData([
"item_qty": FieldValue.increment( Int64(deltaQty) )
], completion: { err in
if let err = err {
print("Error updating document: \(err.localizedDescription)")
} else {
print("Item successfully created with initial quantity")
}
})
}
})
}
Pass in an item number and the quantity to either modify the existing qty by, or will be the initial quantity.
self.incrementQty(itemNumberToUpdate: "item_0", deltaQty: 5)