Share sheet (UIActivityViewController) in iOS Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

What happens when you present UIActivityViewController without excluding any activity types?

You create and present a UIActivityViewController with a text string to share, but you do not set any excludedActivityTypes. What will the user see?

iOS Swift

let textToShare = "Hello from my app!"
let activityVC = UIActivityViewController(activityItems: [textToShare], applicationActivities: nil)
present(activityVC, animated: true)

A The share sheet shows only the default iOS apps like Messages and Mail, excluding third-party apps.

B The share sheet shows all available sharing options including Messages, Mail, and social media apps installed.

C The share sheet shows no options because excludedActivityTypes is nil.

D The app crashes because excludedActivityTypes must be set before presenting.

💡 Hint

Think about what happens if you don't limit or exclude any sharing options.

If you do not set excludedActivityTypes, the UIActivityViewController shows all available sharing options installed on the device, including third-party apps.

📝 Syntax

intermediate

Which code snippet correctly excludes the AirDrop option from the share sheet?

You want to present a UIActivityViewController but exclude the AirDrop option. Which code snippet does this correctly?

A

activityVC.excludedActivityTypes = [.airDrop]
present(activityVC, animated: true)

B

activityVC.excludedActivityTypes = .airDrop
present(activityVC, animated: true)

C

activityVC.excludedActivityTypes = ["airDrop"]
present(activityVC, animated: true)

D

activityVC.excludedActivityTypes = [UIActivity.ActivityType.airDrop]
present(activityVC, animated: true)

💡 Hint

Check the correct enum type and syntax for excludedActivityTypes.

excludedActivityTypes expects an array of UIActivity.ActivityType values. The correct syntax uses the enum with the full type name.

❓ lifecycle

advanced

What happens if you present UIActivityViewController on iPad without setting popoverPresentationController sourceView?

You present a UIActivityViewController on an iPad but forget to set the popoverPresentationController's sourceView or barButtonItem. What is the expected behavior?

iOS Swift

let text = "Check this out!"
let activityVC = UIActivityViewController(activityItems: [text], applicationActivities: nil)
present(activityVC, animated: true)

A The share sheet appears but with a warning in the console only.

B The share sheet appears centered on the screen without any issues.

C The app crashes with a runtime exception about missing popover sourceView.

D The share sheet does not appear and the app freezes.

💡 Hint

iPad requires a popover anchor for modal presentations like UIActivityViewController.

On iPad, UIActivityViewController must have its popoverPresentationController's sourceView or barButtonItem set, otherwise the app crashes at runtime.

❓ navigation

advanced

How to dismiss UIActivityViewController programmatically after sharing completes?

You want to dismiss the UIActivityViewController automatically after the user finishes sharing. Which approach correctly detects completion and dismisses it?

iOS Swift

let activityVC = UIActivityViewController(activityItems: ["Hello"], applicationActivities: nil)
// What to add here?
present(activityVC, animated: true)

A Set activityVC.completionWithItemsHandler to a closure that calls dismiss(animated: true).

B Set activityVC.delegate = self and implement activityViewControllerDidFinish to dismiss.

C Call dismiss(animated: true) immediately after present(activityVC, animated: true).

D Use NotificationCenter to listen for UIActivityViewControllerDidFinish notification and dismiss.

💡 Hint

UIActivityViewController has a completion handler property for this purpose.

The completionWithItemsHandler closure is called when the user finishes or cancels sharing, allowing you to dismiss the controller programmatically.

🧠 Conceptual

expert

Why should you avoid sharing UIImages directly in UIActivityViewController on iOS 16+?

Starting with iOS 16, sharing UIImages directly in UIActivityViewController can cause issues. What is the recommended approach and why?

A Use file URLs pointing to saved images instead of UIImage objects to avoid memory and performance issues.

B Always convert UIImages to Data before sharing to ensure compatibility with all apps.

C Sharing UIImages directly is recommended for best performance and no issues exist on iOS 16+.

D Wrap UIImages inside a custom UIActivity subclass to fix sharing problems on iOS 16+.

💡 Hint

Think about how large images affect memory and how file URLs can help.

Sharing large UIImages directly can cause memory pressure and crashes. Using file URLs to saved images is more efficient and recommended on iOS 16 and later.

Practice

1. What is the main purpose of UIActivityViewController in an iOS app?

easy

A. To manage app settings

B. To present a share sheet allowing users to share content

C. To create a custom navigation bar

D. To handle background tasks

Solution

1. Step 1: Understand the role of UIActivityViewController

   UIActivityViewController is designed to present a share sheet for sharing content.

2. Step 2: Compare with other options

   Options A, B, and D relate to different app functions not handled by UIActivityViewController.

3. Final Answer:

   To present a share sheet allowing users to share content -> Option B

4. Quick Check:

   Share sheet = UIActivityViewController [OK]

Hint: UIActivityViewController always shows sharing options [OK]

Common Mistakes:

• Confusing UIActivityViewController with navigation or settings controllers
• Thinking it manages background tasks
• Assuming it customizes UI elements beyond sharing

2. Which of the following is the correct way to initialize a UIActivityViewController with a text string to share?

easy

A. UIActivityViewController(activityItems: ["Hello World"], applicationActivities: nil)

B. UIActivityViewController(items: "Hello World")

C. UIActivityViewController(shareItems: ["Hello World"])

D. UIActivityViewController(content: "Hello World")

Solution

1. Step 1: Recall the initializer signature

   The correct initializer is UIActivityViewController(activityItems: [Any], applicationActivities: [UIActivity]?).

2. Step 2: Match the correct syntax

   UIActivityViewController(activityItems: ["Hello World"], applicationActivities: nil) matches the correct syntax with an array of items and nil for activities.

3. Final Answer:

   UIActivityViewController(activityItems: ["Hello World"], applicationActivities: nil) -> Option A

4. Quick Check:

   Initializer uses activityItems array [OK]

Hint: Use activityItems array to pass share content [OK]

Common Mistakes:

• Passing a single string instead of an array
• Using wrong parameter names like items or shareItems
• Omitting applicationActivities parameter

3. Given the code snippet below, what will happen when the button is tapped?

let textToShare = "Check this out!"
let activityVC = UIActivityViewController(activityItems: [textToShare], applicationActivities: nil)
present(activityVC, animated: true)

medium

A. The text is copied automatically to clipboard

B. The app crashes due to missing delegate

C. A share sheet appears allowing the user to share the text

D. Nothing happens because the share sheet is not presented

Solution

1. Step 1: Analyze the code behavior

   The code creates a UIActivityViewController with a text item and presents it modally.

2. Step 2: Understand UIActivityViewController presentation

   Presenting it modally shows the share sheet with sharing options for the text.

3. Final Answer:

   A share sheet appears allowing the user to share the text -> Option C

4. Quick Check:

   Presenting UIActivityViewController shows share sheet [OK]

Hint: Presenting UIActivityViewController shows share sheet [OK]

Common Mistakes:

• Assuming delegate is required to present share sheet
• Thinking share sheet appears automatically without present()
• Confusing share sheet with clipboard copy

4. Identify the error in the following code that tries to present a share sheet:

let image = UIImage(named: "photo.png")
let activityVC = UIActivityViewController(activityItems: [image], applicationActivities: nil)
present(activityVC, animated: true)

medium

A. present() must be called on the activityVC instance

B. UIActivityViewController requires a delegate to present

C. The activityItems parameter must be a single item, not an array

D. UIImage named "photo.png" may be nil

Solution

1. Step 1: Check UIImage initialization

   UIImage(named:) returns an optional and may be nil if the image is missing.

2. Step 2: Understand impact on activityItems

   Passing nil in activityItems array results in no shareable content.

3. Final Answer:

   UIImage named "photo.png" may be nil -> Option D

4. Quick Check:

   UIImage(named:) can be nil if image missing [OK]

Hint: Always unwrap UIImage before sharing [OK]

Common Mistakes:

• Assuming delegate is required for UIActivityViewController
• Passing single item instead of array to activityItems
• Calling present() on wrong object

5. You want to share both a URL and a text message using UIActivityViewController. Which code snippet correctly sets this up and presents the share sheet?

hard

A. let url = URL(string: "https://example.com")!
let message = "Check this out!"
let activityVC = UIActivityViewController(activityItems: [url, message], applicationActivities: nil)
present(activityVC, animated: true)

B. let url = URL(string: "https://example.com")
let message = "Check this out!"
let activityVC = UIActivityViewController(activityItems: url, applicationActivities: message)
present(activityVC, animated: true)

C. let url = URL(string: "https://example.com")!
let message = "Check this out!"
let activityVC = UIActivityViewController(items: [url, message])
present(activityVC, animated: true)

D. let url = URL(string: "https://example.com")!
let message = "Check this out!"
let activityVC = UIActivityViewController(activityItems: [message], applicationActivities: [url])
present(activityVC, animated: true)

Solution

1. Step 1: Verify correct initializer usage

   UIActivityViewController requires activityItems as an array of items to share and applicationActivities as optional custom activities.

2. Step 2: Check each option's parameters

   let url = URL(string: "https://example.com")! let message = "Check this out!" let activityVC = UIActivityViewController(activityItems: [url, message], applicationActivities: nil) present(activityVC, animated: true) correctly passes an array with URL and text, and nil for applicationActivities.

3. Step 3: Confirm safe URL unwrapping

   let url = URL(string: "https://example.com")! let message = "Check this out!" let activityVC = UIActivityViewController(activityItems: [url, message], applicationActivities: nil) present(activityVC, animated: true) force unwraps URL safely assuming it exists, which is common in examples.

4. Final Answer:

   let url = URL(string: "https://example.com")! let message = "Check this out!" let activityVC = UIActivityViewController(activityItems: [url, message], applicationActivities: nil) present(activityVC, animated: true) -> Option A

5. Quick Check:

   Pass array of items to activityItems [OK]

Hint: Pass all share items in activityItems array [OK]

Common Mistakes:

• Passing items or applicationActivities incorrectly
• Not using an array for activityItems
• Confusing applicationActivities with share content