SwiftUI 如何从 ObservableObject class 切换结构中的 Bool 并显示警报以通知用户

Question

我的 class 中有一个方法可以在给定地址字符串时打开地图。尝试通过在 class 的方法中切换布尔值来在视图中显示警报。我不知道如何在 class 方法中切换布尔值。这就是我尝试过的。 class 方法中的 Published bool 更新但不在视图中更新。如果有人想使用它，我确实提供了这个功能的回购协议。

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

import SwiftUI

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

}

这是我的 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)
        }
        
    }
}

视图如下：

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")))
            }
    }
}

Answer 1

我更新了这个答案以反映我从@rlong405 那里得到的一些重构帮助我用这个解决方案建立了一个存储库也许它可以帮助其他人。 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)
        }
        
    }
}

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