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.

Practice

1. What is the main purpose of using enum with associated values in Swift?

easy

A. To store extra data along with each enum case

B. To create a class with multiple methods

C. To define global constants

D. To write loops more efficiently

Solution

1. Step 1: Understand enum basics

   An enum groups related values under one type.

2. Step 2: Recognize associated values role

   Associated values let each case hold extra data, like a number or string.

3. Final Answer:

   To store extra data along with each enum case -> Option A

4. Quick Check:

   Enums with associated values store extra data [OK]

Hint: Remember: associated values add data to enum cases [OK]

Common Mistakes:

• Confusing enums with classes
• Thinking enums only hold fixed values
• Mixing associated values with raw values

2. Which of the following is the correct syntax to define an enum case with an associated value of type String?

easy

A. case name = String

B. case name(String)

C. case name: String

D. case name -> String

Solution

1. Step 1: Recall enum case syntax with associated values

   Use parentheses after the case name to specify the type of associated value.

2. Step 2: Match correct syntax

   Only case name(String) uses parentheses correctly.

3. Final Answer:

   case name(String) -> Option B

4. Quick Check:

   Use parentheses for associated value types [OK]

Hint: Use parentheses to declare associated value types [OK]

Common Mistakes:

• Using colon instead of parentheses
• Assigning value with equals sign
• Using arrow notation

3. Given the enum and code below, what will be printed?

enum Result {
  case success(String)
  case failure(Int)
}

let result = Result.success("Done")
switch result {
case .success(let message):
  print(message)
case .failure(let code):
  print("Error \(code)")
}

medium

A. failure

B. Error Done

C. Done

D. Error 0

Solution

1. Step 1: Identify enum case used

   The variable result is .success("Done").

2. Step 2: Follow switch matching

   The switch matches .success(let message) and prints the message "Done".

3. Final Answer:

   Done -> Option C

4. Quick Check:

   Matching case prints associated string [OK]

Hint: Match enum cases to print associated values [OK]

Common Mistakes:

• Printing the enum case name instead of value
• Confusing success and failure cases
• Not using let to extract associated value

4. What is wrong with this enum and switch code?

enum Direction {
  case up(Int)
  case down(Int)
}

let dir = Direction.up(10)
switch dir {
case .up:
  print("Going up")
case .down:
  print("Going down")
}

medium

A. Switch cases must extract associated values with let

B. Enum cases cannot have associated values

C. Variable dir is not initialized correctly

D. Switch must have a default case

Solution

1. Step 1: Check enum cases with associated values

   Cases up and down have Int associated values.

2. Step 2: Analyze switch cases

   Switch cases .up and .down do not extract the Int value with let, causing a compile error.

3. Final Answer:

   Switch cases must extract associated values with let -> Option A

4. Quick Check:

   Extract associated values in switch cases [OK]

Hint: Always use let to get associated values in switch [OK]

Common Mistakes:

• Ignoring associated values in switch
• Thinking default case is mandatory
• Wrong enum initialization

5. You want to model a network response enum with cases success carrying a String message, failure carrying an Int error code, and loading with no data. Which is the correct enum definition?

hard

A. enum NetworkResponse {
case success(String)
case failure(String)
case loading(Int)
}

B. enum NetworkResponse {
case success
case failure
case loading
}

C. enum NetworkResponse {
case success(String, Int)
case failure(Int)
case loading
}

D. enum NetworkResponse {
case success(String)
case failure(Int)
case loading
}

Solution

1. Step 1: Match each case with correct associated value

   success needs a String, failure an Int, loading no data.

2. Step 2: Check each option

   enum NetworkResponse { case success(String) case failure(Int) case loading } matches exactly: success(String), failure(Int), loading without value.

3. Final Answer:

   enum NetworkResponse { case success(String) case failure(Int) case loading } -> Option D

4. Quick Check:

   Define cases with correct associated types [OK]

Hint: Match each case to its exact associated value type [OK]

Common Mistakes:

• Adding wrong types to cases
• Combining multiple values in one case incorrectly
• Assigning associated values to cases that should have none