Passing data from UIViewRepresentable function to SwiftUI View - swift

Question

The user looks for the delivery address on the map, then the address is identified by the marker located in the middle of the screen. And then the address is obtained through this marker. How to display an address in the user interface ?
struct MapView: UIViewRepresentable {
#Binding var centerCoordinate: CLLocationCoordinate2D
var currentLocation: CLLocationCoordinate2D?
var withAnnotation: MKPointAnnotation?
class Coordinator: NSObject, MKMapViewDelegate {
var parent: MapView
var addressLabel: String = "222"
init(_ parent: MapView) {
self.parent = parent
}
func mapViewDidChangeVisibleRegion(_ mapView: MKMapView) {
if !mapView.showsUserLocation {
parent.centerCoordinate = mapView.centerCoordinate
}
}
...
func mapView(_ mapView: MKMapView, regionDidChangeAnimated animated: Bool){
let center = getCenterLocation(for: mapView)
let geoCoder = CLGeocoder()
geoCoder.reverseGeocodeLocation(center) { [weak self] (placemarks, error) in
guard let self = self else { return }
if let _ = error {
//TODO: Show alert informing the user
print("error")
return
}
guard let placemark = placemarks?.first else {
//TODO: Show alert informing the user
return
}
let streetNumber = placemark.subThoroughfare ?? ""
let streetName = placemark.thoroughfare ?? ""
DispatchQueue.main.async {
self.addressLabel = String("\(streetName) | \(streetNumber)")
print(self.addressLabel)
}
}
}
}
func makeCoordinator() -> Coordinator {
Coordinator(self)
}
func makeUIView(context: Context) -> MKMapView {
let mapView = MKMapView()
mapView.delegate = context.coordinator
mapView.showsUserLocation = false
return mapView
}
func updateUIView(_ uiView: MKMapView, context: Context) {
if let currentLocation = self.currentLocation {
if let annotation = self.withAnnotation {
uiView.removeAnnotation(annotation)
}
uiView.showsUserLocation = true
let region = MKCoordinateRegion(center: currentLocation, latitudinalMeters: 1000, longitudinalMeters: 1000)
uiView.setRegion(region, animated: true)
} else if let annotation = self.withAnnotation {
uiView.removeAnnotations(uiView.annotations)
uiView.addAnnotation(annotation)
}
}
}
I am trying to pass the address to the UI.
What's the most correct way to do this?
In the interface, I want to get the address from an ever-changing variable addressLabel
import SwiftUI
import MapKit
fileprivate let locationFetcher = LocationFetcher()
struct LocationView: View {
#State var centerCoordinate = CLLocationCoordinate2D()
#State var currentLocation: CLLocationCoordinate2D?
#State var annotation: MKPointAnnotation?
var body: some View {
ZStack {
MapView(centerCoordinate: $centerCoordinate, currentLocation: currentLocation, withAnnotation: annotation)
.edgesIgnoringSafeArea([.leading, .trailing, .bottom])
.onAppear(perform: {
locationFetcher.start()
})
}
.overlay(
ZStack {
Text("\(*MapView(centerCoordinate: $centerCoordinate, currentLocation: currentLocation, withAnnotation: annotation).makeCoordinator().addressLabel OMG????*)")
.offset(y: 44)
}
)
}
struct LocationView_Previews: PreviewProvider {
static var previews: some View {
LocationView()
}
}
How can i do this ?
Thanks in advance

Answer 1

Here is one approach. Have a single source of truth that both UIKit and SwiftUI can access.
#available(iOS 15.0, *)
struct LocationView: View {
//It is better to have one source of truth
#StateObject var vm: MapViewModel = MapViewModel()
var body: some View {
ZStack {
MapView(vm: vm)
.edgesIgnoringSafeArea([.leading, .trailing, .bottom])
.onAppear(perform: {
//locationFetcher.start() //No Code provided
})
}
.overlay(
HStack{
Spacer()
Text(vm.addressLabel)
Spacer()
//Using offset is subjective since screen sizes change just center it
}
)
//Sample alert that adapts to what is
.alert(isPresented: $vm.errorAlert.isPresented, error: vm.errorAlert.error, actions: {
if vm.errorAlert.defaultAction != nil{
Button("ok", role: .none, action: vm.errorAlert.defaultAction!)
}
if vm.errorAlert.cancelAction != nil{
Button("cancel", role: .cancel, action: vm.errorAlert.cancelAction!)
}
if vm.errorAlert.defaultAction == nil && vm.errorAlert.cancelAction == nil {
Button("ok", role: .none, action: {})
}
})
}
}
//UIKit and SwiftUI will have access to this ViewModel so all the data can have one souce of truth
class MapViewModel: ObservableObject{
//All the variables live here
#Published var addressLabel: String = "222"
#Published var centerCoordinate: CLLocationCoordinate2D = CLLocationCoordinate2D()
#Published var currentLocation: CLLocationCoordinate2D? = nil
#Published var withAnnotation: MKPointAnnotation? = nil
#Published var annotation: MKPointAnnotation?
//This tuple variable allows you to have a dynamic alert in the view
#Published var errorAlert: (isPresented: Bool, error: MapErrors, defaultAction: (() -> Void)?, cancelAction: (() -> Void)?) = (false, MapErrors.unknown, nil, nil)
//The new alert requires a LocalizedError
enum MapErrors: LocalizedStringKey, LocalizedError{
case unknown
case failedToRetrievePlacemark
case failedToReverseGeocode
case randomForTestPurposes
//Add localizable.strings to you project and add these keys so you get localized messages
var errorDescription: String?{
switch self{
case .unknown:
return "unknown".localizedCapitalized
case .failedToRetrievePlacemark:
return "failedToRetrievePlacemark".localizedCapitalized
case .failedToReverseGeocode:
return "failedToReverseGeocode".localizedCapitalized
case .randomForTestPurposes:
return "randomForTestPurposes".localizedCapitalized
}
}
}
//Presenting with this will ensure that errors keep from gettting lost by creating a loop until they can be presented
func presentError(isPresented: Bool, error: MapErrors, defaultAction: (() -> Void)?, cancelAction: (() -> Void)?, count: Int = 1){
//If there is an alert already showing
if errorAlert.isPresented{
//See if the current error has been on screen for 10 seconds
if count >= 10{
//If it has dismiss it so the new error can be posted
errorAlert.isPresented = false
}
//Call the method again in 1 second
DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
let newCount = count + 1
self.presentError(isPresented: isPresented, error: error, defaultAction: defaultAction, cancelAction: cancelAction, count: newCount)
}
}else{
errorAlert = (isPresented, error, defaultAction, cancelAction)
}
}
}
struct MapView: UIViewRepresentable {
#ObservedObject var vm: MapViewModel
class Coordinator: NSObject, MKMapViewDelegate {
var parent: MapView
init(_ parent: MapView) {
self.parent = parent
}
func mapViewDidChangeVisibleRegion(_ mapView: MKMapView) {
if !mapView.showsUserLocation {
parent.vm.centerCoordinate = mapView.centerCoordinate
}
}
func mapView(_ mapView: MKMapView, regionDidChangeAnimated animated: Bool){
getAddress(center: mapView.centerCoordinate)
//Just to demostrate the error
//You can remove this whenever
#if DEBUG
if Bool.random(){
self.parent.vm.presentError(isPresented: true, error: MapViewModel.MapErrors.randomForTestPurposes, defaultAction: nil, cancelAction: nil)
}
#endif
}
//Gets the addess from CLGeocoder if available
func getAddress(center: CLLocationCoordinate2D){
let geoCoder = CLGeocoder()
geoCoder.reverseGeocodeLocation(CLLocation(latitude: center.latitude, longitude: center.longitude)) { [weak self] (placemarks, error) in
guard let self = self else { return }
if let _ = error {
//TODO: Show alert informing the user
print("error")
self.parent.vm.presentError(isPresented: true, error: MapViewModel.MapErrors.failedToReverseGeocode, defaultAction: nil, cancelAction: nil)
return
}
guard let placemark = placemarks?.first else {
//TODO: Show alert informing the user
self.parent.vm.presentError(isPresented: true, error: MapViewModel.MapErrors.failedToRetrievePlacemark, defaultAction: nil, cancelAction: nil)
return
}
let streetNumber = placemark.subThoroughfare ?? ""
let streetName = placemark.thoroughfare ?? ""
DispatchQueue.main.async {
self.parent.vm.addressLabel = String("\(streetName) | \(streetNumber)")
print(self.parent.vm.addressLabel)
}
}
}
}
func makeCoordinator() -> Coordinator {
Coordinator(self)
}
func makeUIView(context: Context) -> MKMapView {
let mapView = MKMapView()
mapView.delegate = context.coordinator
mapView.showsUserLocation = false
return mapView
}
func updateUIView(_ uiView: MKMapView, context: Context) {
if let currentLocation = vm.currentLocation {
if let annotation = vm.withAnnotation {
uiView.removeAnnotation(annotation)
}
uiView.showsUserLocation = true
let region = MKCoordinateRegion(center: currentLocation, latitudinalMeters: 1000, longitudinalMeters: 1000)
uiView.setRegion(region, animated: true)
} else if let annotation = vm.withAnnotation {
uiView.removeAnnotations(uiView.annotations)
uiView.addAnnotation(annotation)
}
}
}