试图将声音融入Swift的信标区域

Question

我得到"在我的代码中使用未解析的标识符‘播放器’使用信标和区域。对于这个特定的区域，我还希望它播放声音(Siren.wav(。代码如下：

import Combine
import CoreLocation
import SwiftUI
import AVFoundation
class BeaconDetector: NSObject, ObservableObject, CLLocationManagerDelegate {
var objectWillChange =  ObservableObjectPublisher()
var locationManager: CLLocationManager?
var lastDistance = CLProximity.unknown
var player: AVAudioPlayer?
//   var audioPlayer = AVAudioPlayer()

override init() {
super.init()
locationManager = CLLocationManager()
locationManager?.delegate = self
locationManager?.requestWhenInUseAuthorization()
}
func locationManager(_ manager: CLLocationManager, didChangeAuthorization status: CLAuthorizationStatus) {
if status == .authorizedWhenInUse {
if CLLocationManager.isMonitoringAvailable(for: CLBeaconRegion.self) {
if CLLocationManager.isRangingAvailable() {
startScanning()
}
}
}
}
func startScanning() {
let uuid = UUID(uuidString: "00000000-0000-0000-0000-000000000000")!
let constraint = CLBeaconIdentityConstraint(uuid: uuid)
let beaconRegion = CLBeaconRegion(beaconIdentityConstraint: constraint, identifier: "MyBeacon")
locationManager?.startMonitoring(for: beaconRegion)
locationManager?.startRangingBeacons(satisfying: constraint)
}
func locationManager(_ manager: CLLocationManager, didRange beacons: [CLBeacon], satisfying beaconConstraint: CLBeaconIdentityConstraint) {
if let beacon = beacons.first {
update(distance: beacon.proximity)
} else {
update(distance: .unknown)
}
}
func update(distance: CLProximity) {
lastDistance = distance
self.objectWillChange.send()
}
}
struct BigText: ViewModifier {
func body(content: Content) -> some View {
content
.font(Font.system(size: 72, design: .rounded))
.frame(minWidth: 0, maxWidth: .infinity, minHeight: 0, maxHeight: .infinity)
}
}
struct ContentView: View {
@ObservedObject var detector = BeaconDetector()
var body: some View {
if detector.lastDistance == .immediate {
return Text("DANGER TOO CLOSE")
.modifier(BigText())
.background(Color.red)
.edgesIgnoringSafeArea(.all)
func playSound() {
guard let url = Bundle.main.url(forResource: "Siren", withExtension: "wav") else { return }
do {
try AVAudioSession.sharedInstance().setCategory(.playback, mode: .default)
try AVAudioSession.sharedInstance().setActive(true)
player = try AVAudioPlayer(contentsOf: url, fileTypeHint: AVFileType.wav.rawValue)
guard let player = player else { return }
player.play()
}
catch let error {
print(error.localizedDescription)

Answer 1

出现"未解析标识符"错误的原因是playSound()方法中未定义变量player。在Swift语言中，每个变量声明都有一个特定的"作用域"，不能在该作用域之外访问它们。

在这种情况下，player被定义为BeaconDetector类中的成员变量。因为playSound()方法不在同一个变量"作用域"中，所以在尝试访问该变量时会出现该错误。

您可能想阅读本教程，了解变量作用域如何在Swift中工作。