How to call async Firebase Geo Query in Swift - swift

Question

I am using the code given by Firebase for the Geo Query feature which I found from this post here: GeoHash Queries in Firebase with Swift
Right now, I am calling this function in the init of one of my classes, and I need this query to be completed before the rest of my code runs. I believe this is wait async/await comes into play but I am new to this concept and I am having trouble implementing this logic. In the code's current state, my attempt to print the number of Docs at the end will print 0, because that last print statement runs before my query completes. How do I make the code after my query wait until my query has completed?
Example format of the data in Firebase:
geohash:"9mupwu3mkc"
id:"13101C7F-D7FF-4141-BC5A-76602173C096"
lat:33.6863622
lng:-117.8264411
Address:"1 Civic Center Plaza, Irvine CA 92606"
Here is the code:
func getallDocs(radius: Double) {
// Find pickups within 50km of Basecamp
let center = CLLocationCoordinate2D(latitude: 33.9742268, longitude: -118.3947792)
let radiusInKilometers: Double = radius
// Each item in 'bounds' represents a startAt/endAt pair. We have to issue
// a separate query for each pair. There can be up to 9 pairs of bounds
// depending on overlap, but in most cases there are 4.
let queryBounds = GFUtils.queryBounds(forLocation: center,
withRadius: radiusInKilometers)
let queries = queryBounds.compactMap { (any) -> Query? in
guard let bound = any as? GFGeoQueryBounds else { return nil }
return db.collection("pickups")
.order(by: "geohash")
.start(at: [bound.startValue])
.end(at: [bound.endValue])
}
var matchingDocs = [QueryDocumentSnapshot]()
// Collect all the query results together into a single list
func getDocumentsCompletion(snapshot: QuerySnapshot?, error: Error?) -> () {
guard let documents = snapshot?.documents else {
print("Unable to fetch snapshot data. \(String(describing: error))")
return
}
print("\nDocs: Count \(documents.count)")
for document in documents {
let lat = document.data()["lat"] as? Double ?? 0
let lng = document.data()["lng"] as? Double ?? 0
let ownerAddress = document.data()["ownerAddress"] as? String ?? "no address"
let coordinates = CLLocation(latitude: lat, longitude: lng)
let centerPoint = CLLocation(latitude: center.latitude, longitude: center.longitude)
// We have to filter out a few false positives due to GeoHash accuracy, but
// most will match
let distance = GFUtils.distance(from: centerPoint, to: coordinates)
print("ownerAddress: \(ownerAddress), distance: \(distance) \tlat: \(lat), \(lng)")
if distance <= radiusInKilometers {
matchingDocs.append(document)
}
}
}
// After all callbacks have executed, matchingDocs contains the result. Note that this
// sample does not demonstrate how to wait on all callbacks to complete.
for query in queries {
query.getDocuments(completion: getDocumentsCompletion)
}
print("Docs: \(matchingDocs.count)")
}