ios - 将自己作为委托(delegate)传递时的无限循环

Question

我正在围绕 CLLocationManager 创建一个包装器，但我正在努力在我的 View Controller 中初始化包装器 LocationManager。

我的 View Controller 执行以下操作:

class MyVC: UIViewController, CLLocationManagerDelegate {   

    var locationManager: LocationManager? {
        get {
            if self.locationManager == nil {
               self.locationManager = LocationManager(delegate: self)
            }

            return self.locationManager
        }
        set {
            self.locationManager = newValue
        }
    }
    ...
}

想法是仅在实际需要时才初始化 LocationManager。但是我收到了一个 EXC_BAD_ACCESS(code=2... 并且当代码在 if self.locationManager == nil { 处中断时，我的主线程看起来像是一个无限循环。 .. 崩溃前约 175000 次。我的 LocationManager 将我的 View Controller 作为 CLLocationManagerDelegate 作为参数，并将其传递给实际的管理器。

import Foundation
import CoreLocation

class LocationManager {
let delegate: CLLocationManagerDelegate

var locationManager: CLLocationManager? {
    get {
        if self.locationManager == nil {
            let locationManager = CLLocationManager()

            locationManager.delegate = self.delegate
            locationManager.desiredAccuracy = kCLLocationAccuracyBestForNavigation

            self.locationManager = locationManager
        }

        return self.locationManager
    }
    set {
        self.locationManager = newValue
    }
}

init(delegate: CLLocationManagerDelegate) {
    self.delegate = delegate
}

func start() {
    if self.isAuthorized() {
        self.locationManager!.startUpdatingLocation()
    }
}

func stop() {
    self.locationManager!.stopUpdatingLocation()
}

func isAuthorized() -> Bool {
    switch CLLocationManager.authorizationStatus() {
        case .Authorized:
            return true
        default:
            return false
    }
}

func requestAuthorization() {
    self.locationManager!.requestAlwaysAuthorization()
}
}

self 的使用不允许在计算属性中像这样传递吗？

Answer 1

你想要的是像这样的惰性属性

lazy  var locationManager: LocationManager = {
           let manager = LocationManager(delegate: self)
            return manager
        }()

同时将 LocationManager 类中的 locationManager 设置为惰性属性。

lazy var locationManager: CLLocationManager =  {
    let locationManager = CLLocationManager()
    locationManager.delegate = self.delegate
    locationManager.desiredAccuracy = kCLLocationAccuracyBestForNavigation
    return locationManager
}()

你的错误在这里

  var locationManager: LocationManager? {
    get {
        if self.locationManager == nil {
           self.locationManager = LocationManager(delegate: self)
        }

        return self.locationManager
    }
    set {
        self.locationManager = newValue
    }
}

在locationManager的get方法中调用self.locationManager，会陷入死循环