Creating MapView from decoded coordinates - swift - ios

Question

I am setting up a MapView with custom coordinates. Here is my code thus far
var coordModel: AirportModel?
struct MapView: View {
#Binding private var lat: Double
#Binding private var lon: Double
private let initialLatitudinalMetres: Double = coordModel?.airportLat ?? 0
private let initialLongitudinalMetres: Double = coordModel?.airportLong ?? 0
#State private var span: MKCoordinateSpan?
init(lat: Binding<Double>, lon: Binding<Double>) {
_lat = lat
_lon = lon
}
private var region: Binding<MKCoordinateRegion> {
Binding {
let centre = CLLocationCoordinate2D(latitude: lat, longitude: lon)
if let span = span {
return MKCoordinateRegion(center: centre, span: span)
} else {
return MKCoordinateRegion(center: centre, latitudinalMeters: initialLatitudinalMetres, longitudinalMeters: initialLongitudinalMetres)
}
} set: { region in
lat = region.center.latitude
lon = region.center.longitude
span = region.span
}
}
var body: some View {
Map(coordinateRegion: region)
}
}
In the AirportModel, there is a piece of data decoded in Double form called "latitude" and "longitude." I am simply trying to pass these data into the view after they are decoded. Here is my view body:
var body: some View {
ScrollView{
MapView(lat: <#Binding<Double>#>, lon: <#Binding<Double>#>)
.frame(height: 250)
.edgesIgnoringSafeArea(/*#START_MENU_TOKEN#*/.all/*#END_MENU_TOKEN#*/)
}
I have tried putting coordModel?.latitude and coordModel?.longitude in for lat and lon, as well as setting variables above the call. I'm not quite sure where to go now.
Note: I am decoding a bunch of JSON data and every user query results in a different lat/lon pull (over 10000 potential responses). Thanks again!

Answer 1

Use a model that is an ObservableObject:
import Combine
import MapKit
class MapModel: ObservableObject {
var region: MKCoordinateRegion = MKCoordinateRegion(
center: CLLocationCoordinate2D(latitude: 48.687330584, longitude: 9.219832454),
latitudinalMeters: 1000000,
longitudinalMeters: 1000000
) {
willSet {
self.objectWillChange.send()
}
}
// MARK: - test code change center evey 10 seconds
init() {
self.timer = Timer.scheduledTimer(withTimeInterval: 10, repeats: true) { timer in
self.testIndex += 1
self.testIndex %= self.testCoordinates.count
let newCenter = self.testCoordinates[self.testIndex]
let oldSpan = self.region.span
DispatchQueue.main.async {
self.region = MKCoordinateRegion(center: newCenter, span: oldSpan)
}
}
}
let testCoordinates = [
CLLocationCoordinate2D(latitude: 48.687330584, longitude: 9.219832454), // STR
CLLocationCoordinate2D(latitude: 41.297445, longitude: 2.0832941), // BCN
]
var testIndex: Int = 0
var timer: Timer? = nil
}
then create a View that observes your model
import SwiftUI
import MapKit
struct ContentView: View {
#ObservedObject private var mapModel = MapModel()
var body: some View {
Map(coordinateRegion: $mapModel.region)
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
For test reasons I used a timer that simulates updated data from a server.
If you need Annotations, add them to the model and don't forget self.objectWillChange.send() if you change them.