CODEWITHSUNDEEP
swiftswiftui
Marian Pavel
Marian Pavel

Reputation: 2876

How to listen array update or other variable in swift

I am an android developer and I started to learn Swift. So far I managed to do everything I wanted, but I struggle with listening to updates in SwiftUI.

I implemented a service that uses Firestore to read from a database. This service is an ObservableObject. Inside the service, I have a variable that is annotated as @Published:

@Published var events = [Event]()

I have implemented Google Maps and I want to fetch these events and do something with them but I don't know how to listen and do something when the call is done.

Google Maps class:

import SwiftUI
import GoogleMaps

struct GoogleMapsView: UIViewRepresentable {
    
    @ObservedObject var databaseService = DatabaseService()
    
    func makeUIView(context: Self.Context) -> GMSMapView {
        let camera = GMSCameraPosition.camera(withLatitude: 45.764375, longitude: 24.994272, zoom: 6.0)
        let mapView = GMSMapView.map(withFrame: CGRect.zero, camera: camera)
        // Here I think I call .getEvents
        databaseService.getEvents()          
        
        return mapView
    }
    
    func updateUIView(_ mapView: GMSMapView, context: Context) {
        // Listen to events update and update them like this, but I don't know how...

        for event in self.databaseService.events {
            let marker = GMSMarker()
            marker.position = CLLocationCoordinate2D(latitude: event.lat, longitude: event.long)
            marker.title = event.title
            marker.snippet = event.title
            marker.map = mapView
        }
    }
}

struct GoogleMapsView_Previews: PreviewProvider {
    static var previews: some View {
        GoogleMapsView()
    }
}

And my SwiftUI View:

import SwiftUI

struct CommunicationsView: View {
    
    @ObservedObject var databaseService = DatabaseService()
    
    var body: some View {
        TabView() {
            GoogleMapsView()
                .edgesIgnoringSafeArea(.top)
                .tabItem {
                    Image(systemName: "leaf.fill")
                    Text("Campanii")
            }
        }.accentColor(.green)
    }
}

struct CommunicationsView_Previews: PreviewProvider {
    static var previews: some View {
        CommunicationsView()
    }
}

Also, here is my service:

class DatabaseService : ObservableObject {

let db: Firestore
@Published var events = [Event]()

init() {
    db = Firestore.firestore()
}

func getEvents() -> Void {
    var tempoEvents = [Event]()
    db.collection(DatabaseName.CAMPAIGNS.rawValue).getDocuments { (query: QuerySnapshot?, error: Error?) in
        for document in query!.documents {
            let data = document.data()
            let title = data["title"] as? String ?? ""
            let details = data["details"] as? String ?? ""
            let lat = data["lat"] as? Double ?? 0.0
            let long = data["long"] as? Double ?? 0.0
            let date = data["date"] as? Date ?? Date()
            let author = data["author"] as? String ?? ""
            tempoEvents.append(Event(id: document.documentID, title: title, details: details, lat: lat, long: long, date: date, author: author))
        }
        
        self.events.append(contentsOf: tempoEvents)
    }
}
}

Upvotes: 2

Views: 209

Answers (1)

Shehata Gamal
Shehata Gamal

Reputation: 100523

You need to put

 @ObservedObject var databaseService = DatabaseService()

only inside CommunicationsView with

GoogleMapsView(events:self.databaseService.events)

and add a property var events = [Event]() inside GoogleMapsView

struct GoogleMapsView: UIViewRepresentable {
  var events = [Event]()
  ......
  for event in self.events {
  }
}

finally in init of DatabaseService 

init() {
   db = Firestore.firestore()
   self.getEvents()
}

Upvotes: 1

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