从子集合 Firestore 中获取文档 swiftUI

Question

I'm trying to retrieve data from documents in a subCollection in Firestore, but it returns an empty array after executing it.

I tried to do the following.

    @Published var OrdersID = [String]()

    func fetchOrdersID(){
        FirebaseManager.shared.firestore.collection("Users").document(id).collection("OrdersID").getDocuments { snapshot, error in
            guard let documents = snapshot?.documents else {
                print("No documents")
                return
            }
            DispatchQueue.main.async {
                self.OrdersID = documents.map{ d in
                    return d["id"] as? String ?? ""
                }
            }
        }
    }

but still it returns an empty array of OrdersID outside this function, and inside of it returns the proper array list(IMAGE 1 shows this, orders ID is the content of the OrdersID array IMAGE 1 )

Answer 1

You could try escaping with a completion..

  @Published var OrdersID = [String]()

func fetchOrdersID(withCompletion completion: @escaping ((_ orderID: String) -> (Void))) {
    FirebaseManager.shared.firestore.collection("Users").document(id).collection("OrdersID").getDocuments { snapshot, error in
        guard let documents = snapshot?.documents else {
            print("No documents")
            return
        }
        
        let orderID = documents["id"] as? String ?? ""

        completion(orderID)
    }
} 

And then when you go to call, you can add to the OrdersId...

fetchOrdersID { orderID in 
   OrdersID.append(orderID)
}