传递自我代表时的无限循环

Question

I am creating a wrapper around CLLocationManager but am struggling to initialize the wrapper LocationManager in my view controller.

My view controller does the following:

class MyVC: UIViewController, CLLocationManagerDelegate {   

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

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

The idea is to initialize a LocationManager only when it is actually needed. However I'm receiving a EXC_BAD_ACCESS(code=2... and what looks like an endless loop on my main thread as the code breaks at the if self.locationManager == nil { ... ~175000 times before crashing. My LocationManager takes my view controller as a CLLocationManagerDelegate as an argument, passing it along to the actual manager.

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()
}
}

Is use of self not allowed to be passed like this in a computed property?

Answer 1

What you want is a lazy property like this

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

Also set locationManager in LocationManager class to lazy property.

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

Your error is here

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

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

You call self.locationManager in the get method of locationManager ,it will fall in dead loop