swift - 我不明白我的代码中的 Property 'self.heading' not initialized at super.init 调用错误

Question

我创建了一个类来为我的 SwiftUI 应用程序使用 CLLocationManagerDelegate 获取当前标题，但是我有 Property 'self.heading' not initialized at super.init call 错误。我不知道为什么。我认为我不需要指定参数，因为我的类在调用期间不接受任何参数？

我的 LocationManager 类:

class LocationManager: NSObject, CLLocationManagerDelegate, ObservableObject {

  var locationManager: CLLocationManager?
  var objectWillChange = PassthroughSubject<Void, Never>()

  @Published var heading: Double {
    willSet {
      objectWillChange.send()
    }
  }

  override init() {
    super.init()

    locationManager = CLLocationManager()
    locationManager!.delegate = self
    locationManager!.desiredAccuracy = kCLLocationAccuracyBest
    locationManager!.requestWhenInUseAuthorization()
  }

  func locationManager(_ manager: CLLocationManager, didUpdateHeading newHeading: CLHeading) {
    self.heading = newHeading.trueHeading.degreesToRadians
  }

}

Answer 1

必须初始化当前类的所有实例变量之前初始化super。

因此在调用 super.init() 之前向 heading 添加一些初始值，例如:

override init() {
    heading = 0 // Or anything you need
    super.init()

    locationManager = CLLocationManager()
    locationManager!.delegate = self
    locationManager!.desiredAccuracy = kCLLocationAccuracyBest
    locationManager!.requestWhenInUseAuthorization()
}