swiftui - SwiftUI 如何从 ObservableObject 类切换 Struct 中的 Bool 并显示警报以通知用户
问题描述
我的班级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 布尔值会更新,但不会在视图中更新。如果有人想玩它,我确实提出了这个功能的回购。
https://github.com/Ongomobile/LocationTest/tree/main/LocationTest
import SwiftUI
@main
struct LocationTestApp: App {
var body: some Scene {
WindowGroup {
ContentView(location: LocationManager())
}
}
}
这是我的课:
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")))
}
}
}
解决方案
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)
}
}
}
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