Getting Device Location on iOS

This article explains how to obtain the user/device location using CoreLocation, Combine, and SwiftUI on iOS.

Overview

The following code snippet is the class responsible for getting the the user's location:

import Combine
import CoreLocation

class DeviceLocationService: NSObject, CLLocationManagerDelegate, ObservableObject {

    var coordinatesPublisher = PassthroughSubject<CLLocationCoordinate2D, Error>()
    var deniedLocationAccessPublisher = PassthroughSubject<Void, Never>()

    private override init() {
        super.init()
    }
    static let shared = DeviceLocationService()

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

    func requestLocationUpdates() {
        switch locationManager.authorizationStatus {
            
        case .notDetermined:
            locationManager.requestWhenInUseAuthorization()
            
        case .authorizedWhenInUse, .authorizedAlways:
            locationManager.startUpdatingLocation()
            
        default:
            deniedLocationAccessPublisher.send()
        }
    }

    func locationManagerDidChangeAuthorization(_ manager: CLLocationManager) {
        switch manager.authorizationStatus {
            
        case .authorizedWhenInUse, .authorizedAlways:
            manager.startUpdatingLocation()
            
        default:
            manager.stopUpdatingLocation()
            deniedLocationAccessPublisher.send()
        }
    }

    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        guard let location = locations.last else { return }
        coordinatesPublisher.send(location.coordinate)
    }
    
    func locationManager(_ manager: CLLocationManager, didFailWithError error: Error) {
        coordinatesPublisher.send(completion: .failure(error))
    }
}

And this is how the location can be accessed using the coordinatesPublisher:

deviceLocationService.coordinatesPublisher
    .sink { completion in
        print("Handle \(completion) for error and finished subscription.")
    } receiveValue: { coordinates in
        print("Handle \(coordinates)")
    }

See the Implementation and Usage sections for a thorough explanation of how the code works.

Implementation

Create a new file called DeviceLocationService.swift and add the following code:

import Combine
import CoreLocation

// 1
class DeviceLocationService: ObservableObject {

    // 2
    var coordinatesPublisher = PassthroughSubject<CLLocationCoordinate2D, Error>()

    // 3
    private init() {}
    static let shared = DeviceLocationService()

}
  1. ObservableObject allows SwiftUI to be notified when there are updates sent through the publishers.
  2. coordinatesPublisher will be used to continuously send location coordinates or an Error to the call site.
  3. As opposed to using multiple instances of DeviceLocationService, make it a singleton so only one class is attempting to retrieve location updates.

Make DeviceLocationService responsible for handling the CLLocationManagerDelegate methods:

// 1
class DeviceLocationService: NSObject, CLLocationManagerDelegate, ObservableObject {

...

    private override init() {
        super.init()
    }

...

    // 2
    private lazy var locationManager: CLLocationManager = {
        let manager = CLLocationManager()
        // 3
        manager.desiredAccuracy = kCLLocationAccuracyBest
        // 4
        manager.delegate = self
        return manager
    }()

    // 5
    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        guard let location = locations.last else { return }
        coordinatesPublisher.send(location.coordinate)
    }
    
    // 6
    func locationManager(_ manager: CLLocationManager, didFailWithError error: Error) {
        coordinatesPublisher.send(completion: .failure(error))
    }
}
  1. DeviceLocationService needs to subclass NSObject so it can conform to CLLocationManagerDelegate.
  2. CLLocationManager is the object responsible for delivering location-based events using a delegate.
  3. You can choose from several constant values for the desired accuracy: kCLLocationAccuracyBestForNavigation, kCLLocationAccuracyBest, kCLLocationAccuracyNearestTenMeters, kCLLocationAccuracyHundredMeters, kCLLocationAccuracyKilometer, kCLLocationAccuracyThreeKilometers, and kCLLocationAccuracyReduced. Keep in mind that higher accuracy will use more resources and drain the user's battery quicker.
  4. Since DeviceLocationService now conforms to CLLocationManagerDelegate, the locationManager can use it as the delegate for location updates.
  5. The didUpdateLocations delegate method will continuously be called by the locationManager and provide an array of CLLocation objects. The last location in the array will be used to send the coordinates using coordinatesPublisher.
  6. In the event the locationManager fails, an error will be sent through coordinatesPublisher and will end any subscriptions.

Add NSLocationWhenInUseUsageDescription or search for Privacy - Location When In Use Usage Description in the dropdown.

Add NSLocationWhenInUseUsageDescription permission

Create a publisher to handle the "Denied Location Access" state:

// 1
var deniedLocationAccessPublisher = PassthroughSubject<Void, Never>()

  1. deniedLocationAccessPublisher will be used to notify the app in the event that the user removes location access from Settings.
// 1
func requestLocationUpdates() {
    switch locationManager.authorizationStatus {
        
    case .notDetermined:
        locationManager.requestWhenInUseAuthorization()
        
    case .authorizedWhenInUse, .authorizedAlways:
        locationManager.startUpdatingLocation()
        
    default:
        deniedLocationAccessPublisher.send()
    }
}

// 2
func locationManagerDidChangeAuthorization(_ manager: CLLocationManager) {
    switch manager.authorizationStatus {
        
    case .authorizedWhenInUse, .authorizedAlways:
        manager.startUpdatingLocation()
        
    default:
        manager.stopUpdatingLocation()
        deniedLocationAccessPublisher.send()
    }
}
  1. Before attempting to get location updates, the authorization status needs to be determined. If it's not determined, then request permission. If access is granted, then start updating the location. In any other case, send a Void using the deniedLocationAccessPublisher.
  2. This function will be called by the CLLocationManager when the authorization status is updated. Following similar logic to requestLocationUpdates, the location updates will either start or stop.

The DeviceLocationService class is ready to be used in the app to provide location updates.

Usage

In ContentView.swift add the following variables:

// 1
@StateObject var deviceLocationService = DeviceLocationService.shared

// 2
@State var tokens: Set<AnyCancellable> = []

// 3
@State var coordinates: (lat: Double, lon: Double) = (0, 0)
  1. Create a @StateObject variable to access the shared instance of DeviceLocationService.
  2. Create a set to store the sinks that will be created to subscribe to the publishers in DeviceLocationService.
  3. Make a tuple to store the latitude and longitude without the need of importing CoreLocation for the CLLocationCoordinate2D type.

Create two functions that can be used to observe the publishers of DeviceLocationService:

// 1
func observeCoordinateUpdates() {
    deviceLocationService.coordinatesPublisher
        .receive(on: DispatchQueue.main)
        .sink { completion in
            print("Handle \(completion) for error and finished subscription.")
        } receiveValue: { coordinates in
            self.coordinates = (coordinates.latitude, coordinates.longitude)
        }
        .store(in: &tokens)
}

// 2
func observeDeniedLocationAccess() {
    deviceLocationService.deniedLocationAccessPublisher
        .receive(on: DispatchQueue.main)
        .sink {
            print("Handle access denied event, possibly with an alert.")
        }
        .store(in: &tokens)
}
  1. observeCoordinateUpdates is responsible for setting up the subscription to coordinatesPublisher and will update the coordinates property of the ContentView with the values passed from DeviceLocationService.
  2. observeDeniedLocationAccess observes when location access has been denied so the user can be notified with an alert or some other UI of your choosing.

Lastly, update the body with the following code so the coordinates can be shown on screen:

var body: some View {
    // 1
    VStack {
        Text("Latitude: \(coordinates.lat)")
            .font(.largeTitle)
        Text("Longitude: \(coordinates.lon)")
            .font(.largeTitle)
    }
    // 2
    .onAppear {
        observeCoordinateUpdates()
        observeDeniedLocationAccess()
        deviceLocationService.requestLocationUpdates()
    }
}
  1. For simplicity, the coordinates are simply being shown on screen using Text views in a VStack.
  2. Use onAppear to perform all the required function calls as soon as the app starts up.

Build and run. You should now be receiving location updates 📍

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