Enum with switch pattern matching in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define an enum named Direction.

Swift

enum Direction {
    case [1]
    case south
    case east
    case west
}

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

Anorth

Bleft

Cup

Dright

Attempts:

3 left

💡 Hint

Common Mistakes

Using a direction name not listed in the enum cases.

Adding spaces or special characters in the case name.

The enum Direction should have a case named north to represent the four main directions.

2fill in blank

medium

Complete the switch statement to handle the Direction enum.

Swift

func describe(direction: Direction) -> String {
    switch direction {
    case [1]:
        return "Going north"
    default:
        return "Other direction"
    }
}

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

Anorth

Bwest

Ceast

Dsouth

Attempts:

3 left

💡 Hint

Common Mistakes

Using a case that does not exist in the enum.

Forgetting to match the case exactly.

The switch case should match the north case of the Direction enum to return the correct description.

3fill in blank

hard

Fix the error in the switch statement to correctly match the enum cases.

Swift

func action(for direction: Direction) -> String {
    switch direction {
    case .[1]:
        return "Move up"
    case .south:
        return "Move down"
    default:
        return "Stay still"
    }
}

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

Aleft

Bup

Cnorth

Dright

Attempts:

3 left

💡 Hint

Common Mistakes

Using a case name not defined in the enum.

Omitting the dot before the case name.

The enum case should be north to match the Direction enum. Using up causes an error because it is not defined.

4fill in blank

hard

Fill both blanks to create a switch that returns a message for east and west directions.

Swift

func directionMessage(_ dir: Direction) -> String {
    switch dir {
    case .[1]:
        return "Heading east"
    case .[2]:
        return "Heading west"
    default:
        return "Unknown direction"
    }
}

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

Aeast

Bnorth

Cwest

Dsouth

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the east and west cases.

Using cases not defined in the enum.

The switch cases should be east and west to return the correct messages for those directions.

5fill in blank

hard

Fill all three blanks to create a switch that returns a message for north, south, and other directions.

Swift

func travelAdvice(_ direction: Direction) -> String {
    switch direction {
    case .[1]:
        return "Go forward"
    case .[2]:
        return "Go backward"
    default:
        return "Stay put"
    }
}

let dir = Direction.[3]
print(travelAdvice(dir))

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

Anorth

Bsouth

Ceast

Dwest

Attempts:

3 left

💡 Hint

Common Mistakes

Using a direction in dir that is not handled explicitly in the switch.

Mixing up the case names in the switch.

The switch cases should be north and south to return the correct advice. The variable dir is set to north to test the function.

Practice

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

easy

A. To group related values and store extra data in each case

B. To create a class with multiple methods

C. To define a function that returns multiple values

D. To declare a variable that can only hold integers

Solution

1. Step 1: Understand enum basics

   An enum groups related values under one type, making code organized.

2. Step 2: Recognize associated values

   Enums with associated values can store extra data for each case, like a label or number.

3. Final Answer:

   To group related values and store extra data in each case -> Option A

4. Quick Check:

   Enum with associated values = group + extra data [OK]

Hint: Enums group related data with extra info easily [OK]

Common Mistakes:

• Confusing enums with classes
• Thinking enums only hold fixed values
• Assuming enums are functions

2. Which of the following is the correct syntax to match an enum case with associated values using switch in Swift?

easy

A. case .someCase(let value):

B. case someCase = value:

C. case .someCase => value:

D. case someCase(value) {

Solution

1. Step 1: Recall switch case syntax for enums

   In Swift, to match an enum case with associated values, use case .caseName(let variable):.

2. Step 2: Identify correct pattern

   case .someCase(let value): uses the correct dot syntax and binding with let.

3. Final Answer:

   case .someCase(let value): -> Option A

4. Quick Check:

   Switch enum case with let binding = case .someCase(let value): [OK]

Hint: Use dot and let to bind enum associated values [OK]

Common Mistakes:

• Missing dot before case name
• Using = instead of :
• Wrong arrow or braces syntax

3. What will be the output of this Swift code?

enum Direction {
    case north, south, east, west
}

let dir = Direction.east

switch dir {
case .north:
    print("Going North")
case .south:
    print("Going South")
case .east:
    print("Going East")
case .west:
    print("Going West")
}

medium

A. No output

B. Going North

C. Going West

D. Going East

Solution

1. Step 1: Identify enum value assigned

   The variable dir is assigned Direction.east.

2. Step 2: Match switch case

   The switch matches .east case and prints "Going East".

3. Final Answer:

   Going East -> Option D

4. Quick Check:

   dir = east prints "Going East" [OK]

Hint: Match enum value to switch case to find output [OK]

Common Mistakes:

• Confusing enum case names
• Forgetting to include all cases
• Assuming default case runs

4. Identify the error in this Swift code using enum and switch:

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

let res = Result.success(10)

switch res {
case .success(let value):
    print("Value: \(value)")
case failure(let message):
    print("Error: \(message)")
}

medium

A. Switch statement missing default case

B. Wrong associated value type for 'success'

C. Missing dot before 'failure' in switch case

D. Enum cases cannot have associated values

Solution

1. Step 1: Check switch case syntax

   In switch, enum cases must be prefixed with a dot, like .failure.

2. Step 2: Identify missing dot

   The second case uses failure without a dot, causing a syntax error.

3. Final Answer:

   Missing dot before 'failure' in switch case -> Option C

4. Quick Check:

   Enum case in switch needs dot prefix [OK]

Hint: Always prefix enum cases with dot in switch [OK]

Common Mistakes:

• Omitting dot before enum case in switch
• Confusing associated value types
• Forgetting to handle all cases

5. Given this enum and function, what will describeShape(.rectangle(width: 5, height: 10)) print?

enum Shape {
    case circle(radius: Double)
    case rectangle(width: Double, height: Double)
    case point
}

func describeShape(_ shape: Shape) {
    switch shape {
    case .circle(let r):
        print("Circle with radius \(r)")
    case .rectangle(let w, let h):
        print("Rectangle \(w) x \(h)")
    case .point:
        print("Just a point")
    }
}

hard

A. Circle with radius 5.0

B. Rectangle 5.0 x 10.0

C. Just a point

D. Syntax error in switch

Solution

1. Step 1: Identify enum case and associated values

   The input is .rectangle(width: 5, height: 10), so width = 5 and height = 10.

2. Step 2: Match switch case and print

   The switch matches .rectangle(let w, let h) and prints "Rectangle 5.0 x 10.0".

3. Final Answer:

   Rectangle 5.0 x 10.0 -> Option B

4. Quick Check:

   Rectangle case prints dimensions [OK]

Hint: Match enum case and extract all associated values [OK]

Common Mistakes:

• Using wrong variable names in case
• Missing multiple associated values in pattern
• Assuming default case runs