我不明白 Property 'self.heading' not initialized at super.init call error in my code答案

【问题标题】：I don't understand Property 'self.heading' not initialized at super.init call error in my code我不明白 Property 'self.heading' not initialized at super.init call error in my code
【发布时间】：2019-09-15 13:35:05
【问题描述】：

我创建了一个类来使用 CLLocationManagerDelegate 为我的 SwiftUI 应用程序获取当前标题，但出现 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，因为我的类在调用过程中不带任何参数？

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
  }

}

【问题讨论】：

标签： swift cllocationmanager swiftui

【解决方案1】：

您必须在初始化super之前初始化当前类的所有实例变量。

所以在调用super.init() 之前给heading 添加一些初始值，比如：

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

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

【讨论】：