Enums with associated values in iOS Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

What is the output of this Swift enum with associated values?

Consider this Swift code that uses an enum with associated values. What will be printed when the code runs?

iOS Swift

enum Device {
  case iPhone(model: String)
  case iPad(model: String)
}

let myDevice = Device.iPhone(model: "13 Pro")
switch myDevice {
case .iPhone(let model):
  print("Using iPhone model: \(model)")
case .iPad(let model):
  print("Using iPad model: \(model)")
}

A Using iPhone model: 13 Pro

B Compilation error due to missing default case

C Using iPhone model: model

D Using iPad model: 13 Pro

💡 Hint

Look at which case is assigned to myDevice and how the switch extracts the associated value.

The enum instance is created as .iPhone with model "13 Pro". The switch matches .iPhone and prints the model string.

🧠 Conceptual

intermediate

How many associated values does this enum case have?

Look at this Swift enum case declaration. How many associated values does the case 'message' have?

iOS Swift

enum Notification {
  case message(sender: String, content: String)
  case alert(title: String)
}

A One associated value

B Two associated values

C No associated values

D Three associated values

💡 Hint

Count the parameters inside the parentheses after the case name.

The 'message' case has two associated values: sender and content, both Strings.

📝 Syntax

advanced

Which option correctly creates an enum instance with associated values?

Given this enum, which code correctly creates an instance of the 'status' case with associated values?

iOS Swift

enum Network {
  case status(code: Int, message: String)
  case disconnected
}

A let result = Network.status(code: 200, message: "OK")

B let result = Network.status(200, "OK")

C let result = Network.status(code = 200, message = "OK")

D let result = Network.status(code: "200", message: "OK")

💡 Hint

Remember the syntax for creating enum cases with named associated values.

Option A uses the correct syntax with parameter labels and values matching the enum definition.

❓ lifecycle

advanced

What happens if you forget to handle an enum case with associated values in a switch?

Consider this code snippet. What error or behavior occurs if the switch does not handle all enum cases?

iOS Swift

enum Action {
  case start(time: Int)
  case stop
}

let action = Action.start(time: 10)
switch action {
case .stop:
  print("Stopped")
}

A Prints nothing and continues

B Runtime error: Missing case causes crash

C Automatically handles missing cases with default values

D Compilation error: Switch must be exhaustive

💡 Hint

Swift requires all enum cases to be handled or a default case provided.

The switch is not exhaustive because it misses the 'start' case, so the compiler raises an error.

🔧 Debug

expert

Why does this code cause a compile error?

Examine this Swift enum and usage. Why does the compiler report an error?

iOS Swift

enum Result {
  case success(data: String)
  case failure(error: String)
}

let outcome = Result.success("Done")

switch outcome {
case .success:
  print("Success")
case .failure(let error):
  print("Error: \(error)")
}

A Switch cases cannot use 'let' to extract values

B Enum cases must not have associated values

C Missing associated value extraction in '.success' case

D Cannot use string literals as associated values

💡 Hint

Check how the '.success' case is matched and if it extracts the associated value.

The '.success' case has an associated value but the switch does not extract it, causing a compile error.