Enums with associated values in iOS Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an enum with an associated value.

iOS Swift

enum Vehicle {
  case car([1]: String)
}

Drag options to blanks, or click blank then click option'

Amodel

Bspeed

Ccolor

Dyear

Attempts:

3 left

💡 Hint

Common Mistakes

Using a type name instead of a label for the associated value.

Omitting the label before the colon.

The enum case car has an associated value named model of type String.

2fill in blank

medium

Complete the code to extract the associated value from the enum using a switch statement.

iOS Swift

let vehicle = Vehicle.car(model: "Sedan")
switch vehicle {
case .car(let [1]):
  print("Model is \(model)")
}

Drag options to blanks, or click blank then click option'

Atype

Bname

Cmodel

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different variable name than the associated value label.

Forgetting to use let to bind the value.

The let model extracts the associated value labeled model from the enum case.

3fill in blank

hard

Fix the error in the enum declaration by completing the associated value syntax.

iOS Swift

enum Result {
  case success([1] Int)
  case failure(String)
}

Drag options to blanks, or click blank then click option'

Astatus

Bcode

Cerror:

Dvalue:

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the colon after the label.

Using a label without colon or just the type.

The associated value must have a label followed by a colon, like value:.

4fill in blank

hard

Fill both blanks to declare an enum case with two associated values.

iOS Swift

enum Message {
  case text([1]: String, [2]: Int)
}

Drag options to blanks, or click blank then click option'

Acontent

Blength

Csize

Dtext

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same label twice.

Omitting the colon after labels.

The enum case text has two associated values labeled content and length.

5fill in blank

hard

Fill all three blanks to create a dictionary from an enum with associated values filtering by a condition.

iOS Swift

let messages = [
  Message.text(content: "Hi", length: 2),
  Message.text(content: "Hello", length: 5),
  Message.text(content: "Hey", length: 3)
]

let filtered = messages.filter { msg in
  if case .text(let [1], let [2]) = msg {
    return [2] [3] 3
  }
  return false
}

Drag options to blanks, or click blank then click option'

Acontent

Blength

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong labels in the pattern matching.

Using the wrong comparison operator.

The code extracts content and length from each Message.text case and filters messages with length greater than 3.

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