SwiftUI How to toggle a Bool in a Struct from an ObservableObject class and show alert to notify user

Question

I have a method in my class that opens a map when given an address string. Trying to show an alert in a view by toggling a boolean in a method in the class. I can't figure out how to toggle the boolean in the class method. This is what I tried. The Published bool in class method updates but does not update in the View. I did put up a repo of just this feature if anybody wants to play around with it.

https://github.com/Ongomobile/LocationTest/tree/main/LocationTest

import SwiftUI

@main
struct LocationTestApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView(location: LocationManager())
        }
 }

}

Here is my Class:

import UIKit
import MapKit
import CoreLocation
import Combine

class LocationManager: NSObject, ObservableObject {
    var locationManager = CLLocationManager()
    lazy var geocoder = CLGeocoder()
    
    @Published var locationString = "1140"
    // @Published var locationString = "1 apple park way cupertino"
    @Published var currentAddress = ""
    @Published var isValid: Bool = true
    
    
    
    func openMapWithAddress () {
        
        geocoder.geocodeAddressString(locationString) { placemarks, error in
            if let error = error {
                self.isValid = false
                // prints false but does not update
                print("isValid")
                print(error.localizedDescription)
            }
            
            guard let placemark = placemarks?.first else {
                return
            }
            
            guard let lat = placemark.location?.coordinate.latitude else{return}
            
            guard let lon = placemark.location?.coordinate.longitude else{return}
            
            let coords = CLLocationCoordinate2DMake(lat, lon)
            
            let place = MKPlacemark(coordinate: coords)
            
            let mapItem = MKMapItem(placemark: place)
            mapItem.name = self.locationString
            mapItem.openInMaps(launchOptions: nil)
        }
        
    }
}

Here is the view:

import SwiftUI

struct ContentView: View {
@ObservedObject  var locationManager = LocationManager()
@State private var showingAlert = false

var body: some View {
    Button {
        locationManager.openMapWithAddress()
       
    } label: {
        Text("Get Map")
        }
        .alert(isPresented: $showingAlert) {
                Alert(title: Text("Important message"), message: 
                Text("Enter a valid address"), dismissButton: 
                .default(Text("OK")))
            }
    }
}

Here is an example of `.alert` usage https://stackoverflow.com/a/60102640/12299030. Try also to search, there are a lot. — Asperi, Jan 24 '21 at 06:13
Asperi Thanks for your help I edited my question hopefully to be more clear — Mike Haslam, Jan 24 '21 at 19:52

Mike Haslam · Accepted Answer · 2021-01-27T21:12:27.693

I updated this answer to reflect some refactor help that I got from @rlong405 I put up a repository with this solution maybe it could help others. OpenMapsInSwiftUI

import SwiftUI

struct ContentView: View {
    @ObservedObject var locationManager = LocationManager()
    
    
    var body: some View {
        VStack{
            Form{
                Section {
                    Text("Enter Address")
                    TextField("", text: $locationManager.locationString)
                        .textFieldStyle(RoundedBorderTextFieldStyle())
                        .padding(.horizontal)
                }
                Button {
                    locationManager.openMapWithAddress()
                    
                } label: {
                    Text("Get Map")
                }
                .alert(isPresented: $locationManager.invalid) {
                    Alert(title: Text("Important message"), message: 
                    Text("Enter a valid address"), dismissButton: 
                    .default(Text("OK"), action:{
                        locationManager.invalid = false
                        locationManager.locationString = ""
                    }))
                }
            }
        }
    }
}

import UIKit
import MapKit
import CoreLocation
import Combine

class LocationManager: NSObject, ObservableObject {
    lazy var geocoder = CLGeocoder()
    
    @Published var locationString = ""
    @Published var invalid: Bool = false
   
    func openMapWithAddress () {
        
        geocoder.geocodeAddressString(locationString) { placemarks, error in
            if let error = error {
                DispatchQueue.main.async {
                    self.invalid = true
                }
                print(error.localizedDescription)
            }
            
            guard let placemark = placemarks?.first else {
                return
            }
            
            guard let lat = placemark.location?.coordinate.latitude else{return}
            
            guard let lon = placemark.location?.coordinate.longitude else{return}
            
            let coords = CLLocationCoordinate2DMake(lat, lon)
            
            let place = MKPlacemark(coordinate: coords)
            
            let mapItem = MKMapItem(placemark: place)
            mapItem.name = self.locationString
            mapItem.openInMaps(launchOptions: nil)
        }
        
    }
}

SwiftUI How to toggle a Bool in a Struct from an ObservableObject class and show alert to notify user

1 Answers1