Location services (Core Location) in iOS Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

What is the output when location updates are received?

Consider this Swift code snippet using Core Location. What will be printed when the device location updates?

iOS Swift

import CoreLocation

class LocationHandler: NSObject, CLLocationManagerDelegate {
  let manager = CLLocationManager()

  override init() {
    super.init()
    manager.delegate = self
    manager.requestWhenInUseAuthorization()
    manager.startUpdatingLocation()
  }

  func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
    if let location = locations.last {
      print("Lat: \(location.coordinate.latitude), Lon: \(location.coordinate.longitude)")
    }
  }
}

A Prints an error message because delegate is not set.

B Prints the initial authorization status only.

C Prints nothing because startUpdatingLocation() is not called.

D Prints the latest latitude and longitude coordinates when location updates arrive.

💡 Hint

Check what happens inside the didUpdateLocations delegate method.

The delegate method didUpdateLocations is called when new location data arrives. The code prints the last location's latitude and longitude.

🧠 Conceptual

intermediate

What permission is required to access location in foreground?

Which key must be added to Info.plist to request permission for location access only when the app is in use?

A NSLocationWhenInUseUsageDescription

B NSLocationAlwaysUsageDescription

C NSLocationTemporaryUsageDescription

D NSLocationBackgroundUsageDescription

💡 Hint

Think about the permission that allows location only during app use.

NSLocationWhenInUseUsageDescription is the key to request location access only when the app is active in the foreground.

❓ lifecycle

advanced

What happens if you call stopUpdatingLocation() too early?

Given this code snippet, what is the effect of calling stopUpdatingLocation() immediately after startUpdatingLocation()?

iOS Swift

manager.startUpdatingLocation()
manager.stopUpdatingLocation()

A Location updates will continue indefinitely despite stop call.

B No location updates will be received because updates stop immediately.

C App crashes due to invalid state transition.

D Location updates start but only one update is received.

💡 Hint

Consider the effect of stopping updates right after starting.

Calling stopUpdatingLocation() right after startUpdatingLocation() cancels location updates immediately, so no updates are delivered.

🔧 Debug

advanced

Why does this code not print location updates?

This code does not print location updates as expected. What is the most likely cause?

iOS Swift

class LocationManager: NSObject, CLLocationManagerDelegate {
  let manager = CLLocationManager()

  override init() {
    super.init()
    manager.requestWhenInUseAuthorization()
    manager.startUpdatingLocation()
  }

  func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
    print("Location updated")
  }
}

A The delegate property is not set, so delegate methods are not called.

B Authorization request is missing, so updates are blocked.

C startUpdatingLocation() is called before authorization request.

D didUpdateLocations method signature is incorrect.

💡 Hint

Check if the delegate is assigned properly.

Without setting manager.delegate = self, the delegate methods won't be called, so no location updates are printed.

❓ navigation

expert

How to navigate to app settings for location permission?

Which code snippet correctly opens the app's settings page so the user can change location permissions?

A UIApplication.shared.open(URL(string: "settings://")!)

B UIApplication.shared.open(URL(string: "app-settings://")!)

C

if let url = URL(string: UIApplication.openSettingsURLString) {
  UIApplication.shared.open(url)
}

D UIApplication.shared.open(URL(string: "prefs:root=LOCATION_SERVICES")!)

💡 Hint

Use the official constant for opening app settings.

UIApplication.openSettingsURLString is the official URL string to open the app's settings page. Other URLs are deprecated or invalid.