Load data from Firebase once - ios

Question

I am using Firebase as my backend service & fetching data using the SnapshotListener ( which keep listening for any data changes ). I want to remove that listener (only run and fetch data on first load).
private func loadShops(_ category: String) {
db.collection(category).addSnapshotListener { snapshot, error in
guard error == nil else {
print(error!.localizedDescription)
return
}
if let docs = snapshot?.documents {
for doc in docs {
self.shops = []
let shopData = doc.data()
var newShop = Shop()
newShop.shopName = shopData["name"] as? String ?? "Empty Name"
self.shops.append(newShop)
self.shops.shuffle()
}
self.shopsView.tableView.reloadData()
}
}
}

Answer 1

Based on the API example above - I'm assuming you are using the Firestore API and not the older Firebase.
If its firestore, you could just use query fetch instead of using a snapshot listener.
Refer to https://firebase.google.com/docs/firestore/query-data/queries#execute_a_query
private func loadShops(_ category: String) {
db.collection(category).getDocuments() { (querySnapshot, err) in
if let err = err {
print("Error getting documents: \(err)")
} else if let querySnapshot = querySnapshot {
for document in querySnapshot.documents {
print("\(document.documentID) => \(document.data())")
// do the conversion to model object.
}
}
}
Using the snapshot listener is only if you want to continue monitoring the cloud for new documents. It is also costly as per the pricing documentation.