Firebase Tasks in Swift / iOS

Question

I'm an android developer learning to write my app for iOS using swift. I'm unsure how to run multiple firebase (firestore and realtime database) write tasks asynchronous and return a completion handler. In android I use the Tasks API and have it written as follows:

Task<Void> firestoreTask = firestoreDB.getDocument("users/someId").update("name", "some name");

Task<Void> realtimeTask = realtimeDB.child("users/someId/name/").setValue("some name");

Tasks.whenAll(firestoreTask, realtimeTask).addOnSuccessListener(new OnSuccessListener<Void>() {
            @Override
            public void onSuccess(Void aVoid) {
                // if both tasks are successful
            }
        })
        .addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                // if at least one of the two task fails
            }
        });

I can't seem to figure out how to write such a task in swift. Can someone please point me in the right direction? Thank you.

I don't know Android well, but I assume what you're trying to do is perform two different asynchronous requests and have a callback when they're finished? — Eilon, Feb 17 '20 at 12:31
Correct. The tasks cannot run independently, because I can't have one task fail and the other succeed based on the database security rules. If one task fails then the other should as well. — TrackDave, Feb 17 '20 at 13:14
A quick [search](https://www.google.com/search?q=swift+wait+for+multiple+callbacks) leads to [Synchronise Multiple Async Tasks With Dispatch Groups](https://dispatchswift.com/introduction-to-dispatch-group-a5cf9d61ff4f) and https://stackoverflow.com/questions/35906568/wait-until-swift-for-loop-with-asynchronous-network-requests-finishes-executing — Frank van Puffelen, Feb 17 '20 at 14:13

score 2 · Accepted Answer · answered Feb 17 '20 at 15:43

Following code will help you to solve this problem

import Foundation

// Create a dispatch group object and add a didset observer to catch error in operation

var dispatchGroup:DispatchGroup? = DispatchGroup(){
    didSet{
        if dispatchGroup == nil{
            // here you can do whetever after at least one of the two task fails
            print("error in FirestoreTask or realtimeTask")
        }
    }
}

// do your firestoreTask in this method
func dofirestoreTask (){
    // Implement your firestore task here //

    let taskResponse = true // Remove this variable with your firestore task response status
    if taskResponse == true{
        dispatchGroup?.leave()
    }else{
        dispatchGroup = nil
    }
}

func dorealtimeTask(){
    // Implement your realTimeTask here task here //
    let taskResponse = true // Remove this variable with your realTime task response status
    if taskResponse == true{
        dispatchGroup?.leave()
    }else{
        dispatchGroup = nil
    }
}

dispatchGroup?.enter()
dofirestoreTask()
dispatchGroup?.enter()
dorealtimeTask()

dispatchGroup?.notify(queue: .main) {
    // here you can do whetever after both tasks are successful
    print("Both Success")
}

score 0 · Answer 2 · answered Feb 17 '20 at 12:30

0

I think in iOS you have only closures.

answered Feb 17 '20 at 12:30

mkowal87

596
4
19

Firebase Tasks in Swift / iOS

2 Answers2