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

问题描述

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

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

import SwiftUI

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

}

这是我的班级：

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)
        }
        
    }
}

这是视图：

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")))
            }
    }
}

解决方法

我更新了这个答案以反映我从@rlong405 获得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)
        }
        
    }
}