Camera and photo library in iOS Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

What happens when UIImagePickerController sourceType is set to .camera?

Consider this Swift code snippet in an iOS app:

let picker = UIImagePickerController()
picker.sourceType = .camera
present(picker, animated: true)

What will the user see after this code runs?

iOS Swift

let picker = UIImagePickerController()
picker.sourceType = .camera
present(picker, animated: true)

A The app shows an error because .camera is not a valid sourceType.

B The app opens the photo library for the user to select an existing photo.

C The app opens the device camera interface allowing the user to take a photo.

D The app opens a blank screen with no controls.

💡 Hint

Think about what .camera means in UIImagePickerController.

Setting sourceType to .camera tells the app to open the device's camera interface so the user can take a new photo.

🧠 Conceptual

intermediate

Why must you check UIImagePickerController.isSourceTypeAvailable before using .camera?

In iOS development, before setting UIImagePickerController's sourceType to .camera, why should you check if the camera is available using isSourceTypeAvailable(.camera)?

A Because some devices or simulators do not have a camera, and trying to use it without checking causes a crash.

B Because it automatically requests camera permission from the user.

C Because it improves app performance by preloading the camera hardware.

D Because it changes the camera resolution settings.

💡 Hint

Think about devices like iPads without cameras or simulators.

Not all devices have a camera. Checking availability prevents the app from crashing when trying to access a missing camera.

❓ lifecycle

advanced

What delegate method is called after a user picks a photo from the library?

When using UIImagePickerController to let the user pick a photo from the photo library, which delegate method is called after the user selects a photo?

A imagePickerController(_:didFinishPickingMediaWithInfo:)

B imagePickerControllerDidCancel(_:)

C applicationDidBecomeActive(_:)

D viewDidLoad()

💡 Hint

This method provides the selected image info.

The delegate method imagePickerController(_:didFinishPickingMediaWithInfo:) is called when the user finishes picking a photo.

🔧 Debug

advanced

Why does this code crash when accessing the photo library?

Given this Swift code snippet:

let picker = UIImagePickerController()
picker.sourceType = .photoLibrary
present(picker, animated: true)

The app crashes on devices running iOS 14 or later. What is the most likely cause?

iOS Swift

let picker = UIImagePickerController()
picker.sourceType = .photoLibrary
present(picker, animated: true)

A The present method requires a completion handler.

B The sourceType .photoLibrary is not supported on iOS 14 or later.

C UIImagePickerController must be presented inside a navigation controller.

D The app is missing the NSPhotoLibraryUsageDescription key in Info.plist, so iOS denies access.

💡 Hint

Check app permissions in Info.plist.

iOS requires a usage description key in Info.plist to allow photo library access. Missing it causes a crash.

❓ navigation

expert

What is the correct way to dismiss UIImagePickerController after photo selection?

After the user picks a photo using UIImagePickerController, which code snippet correctly dismisses the picker and processes the image?

iOS Swift

func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) {
    // process image
}

A dismiss(animated: true) { /* process image here */ }

B picker.dismiss(animated: true) { /* process image here */ }

C picker.popViewController(animated: true)

D self.navigationController?.dismiss(animated: true)

💡 Hint

Dismiss the picker itself, not the whole view controller.

You must call dismiss on the picker to close it, optionally handling image processing in the completion block.