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.

Practice

1.

What is the main purpose of CLLocationManager in iOS apps?

easy

A. To request and receive location updates from the device

B. To display maps on the screen

C. To manage user notifications

D. To handle network requests

Solution

1. Step 1: Understand the role of CLLocationManager

   CLLocationManager is designed to get location data from the device's GPS or other sources.

2. Step 2: Differentiate from other classes

   Displaying maps is done by MKMapView, notifications by UNUserNotificationCenter, and network requests by URLSession.

3. Final Answer:

   To request and receive location updates from the device -> Option A

4. Quick Check:

   CLLocationManager = Location updates [OK]

Hint: CLLocationManager is for getting location, not showing maps [OK]

Common Mistakes:

• Confusing CLLocationManager with map display classes
• Thinking it handles notifications or networking
• Assuming it works without user permission

2.

Which of the following is the correct way to declare a CLLocationManager instance in Swift?

?

easy

A. locationManager = CLLocationManager()

B. var locationManager: CLLocationManager

C. let locationManager = CLLocationManager()

D. CLLocationManager locationManager = new CLLocationManager()

Solution

1. Step 1: Recall Swift instance creation syntax

   In Swift, to create an instance, use let variable = ClassName() or var variable = ClassName().

2. Step 2: Check each option

   let locationManager = CLLocationManager() correctly creates a constant instance. var locationManager: CLLocationManager declares a variable without initialization, which is incomplete. locationManager = CLLocationManager() misses declaration keyword. CLLocationManager locationManager = new CLLocationManager() uses incorrect syntax from other languages.

3. Final Answer:

   let locationManager = CLLocationManager() -> Option C

4. Quick Check:

   Swift instance creation = let variable = Class() [OK]

Hint: Use let or var with = ClassName() to create instances [OK]

Common Mistakes:

• Forgetting to initialize the variable
• Using syntax from other languages like Java or C#
• Missing let or var keyword

3.

Given the following Swift code snippet, what will be printed when the location updates?

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.first {
      print("Lat: \(location.coordinate.latitude), Lon: \(location.coordinate.longitude)")
    }
  }
}
let handler = LocationHandler()

medium

A. It crashes due to missing delegate method

B. It prints the latitude and longitude of the first location update

C. It prints nothing because delegate is not set

D. It prints an error message about missing permissions

Solution

1. Step 1: Analyze delegate setup and method

   The delegate is set to self, and the required method locationManager(_:didUpdateLocations:) is implemented to print coordinates.

2. Step 2: Understand permission and update calls

   The code requests permission and starts location updates, so when location is available, it prints latitude and longitude.

3. Final Answer:

   It prints the latitude and longitude of the first location update -> Option B

4. Quick Check:

   Delegate set + method implemented = prints location [OK]

Hint: Delegate method prints first location coordinates on update [OK]

Common Mistakes:

• Assuming delegate is not set
• Thinking permission request blocks printing
• Missing delegate method causes crash

4.

What is wrong with this Swift code snippet for requesting location updates?

let locationManager = CLLocationManager()
locationManager.startUpdatingLocation()

medium

A. It is missing setting the delegate and requesting user permission

B. startUpdatingLocation() is not a valid method

C. locationManager must be declared as a class, not a constant

D. The code should call stopUpdatingLocation() first

Solution

1. Step 1: Check for permission request

   The code does not request user permission, which is required before starting location updates.

2. Step 2: Check delegate assignment

   Without setting a delegate, the app cannot receive location updates callbacks.

3. Final Answer:

   It is missing setting the delegate and requesting user permission -> Option A

4. Quick Check:

   Permission + delegate needed before updates [OK]

Hint: Always request permission and set delegate before updates [OK]

Common Mistakes:

• Calling startUpdatingLocation without permission
• Not assigning delegate to receive updates
• Thinking startUpdatingLocation is invalid

5.

You want your app to get the user's location only once and then stop updates to save battery. Which code snippet correctly does this?

class SingleLocationFetcher: 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.first {
      print("Got location: \(location.coordinate.latitude), \(location.coordinate.longitude)")
      manager.stopUpdatingLocation()
    }
  }
}

hard

A. This code will crash because stopUpdatingLocation is not a valid method

B. This code will never stop updates because stopUpdatingLocation is called too early

C. This code requests background location permission incorrectly

D. This code correctly stops updates after receiving the first location

Solution

1. Step 1: Check when stopUpdatingLocation is called

   The method locationManager(_:didUpdateLocations:) calls stopUpdatingLocation() after receiving the first location, stopping further updates.

2. Step 2: Verify permission and delegate setup

   The code requests 'when in use' authorization and sets the delegate properly, so it will work as intended.

3. Final Answer:

   This code correctly stops updates after receiving the first location -> Option D

4. Quick Check:

   Stop updates inside didUpdateLocations = single fetch [OK]

Hint: Call stopUpdatingLocation inside didUpdateLocations after first fix [OK]

Common Mistakes:

• Calling stopUpdatingLocation before receiving location
• Confusing background permission with when-in-use
• Not setting delegate before starting updates