Enum declaration and cases in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an enum named Direction.

Swift

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

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

AMove

Bdirection

CDirection

DDirections

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase for enum name

Using plural form which is not the given enum name

The enum name should be Direction with a capital D as per Swift naming conventions.

2fill in blank

medium

Complete the code to add a case named 'up' to the enum.

Swift

enum Movement {
    case [1]
    case down
}

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

Aright

Bleft

Cforward

Dup

Attempts:

3 left

💡 Hint

Common Mistakes

Using uppercase letters for case names

Choosing a wrong direction name

The case to add is up as specified.

3fill in blank

hard

Fix the error in the enum case declaration.

Swift

enum Color {
    case [1]
}

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

Ared

BRED

CRed

DrEd

Attempts:

3 left

💡 Hint

Common Mistakes

Using uppercase letters for enum cases

Using mixed case which is not standard

Enum cases in Swift should be lowercase, so red is correct.

4fill in blank

hard

Fill both blanks to declare an enum with two cases: 'spring' and 'fall'.

Swift

enum Season {
    case [1]
    case [2]
}

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

Aspring

Bsummer

Cfall

Dwinter

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong season names

Using uppercase letters

The enum Season has cases spring and fall as requested.

5fill in blank

hard

Fill all three blanks to declare an enum with cases 'small', 'medium', and 'large'.

Swift

enum Size {
    case [1]
    case [2]
    case [3]
}

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

Asmall

Bmedium

Clarge

DextraLarge

Attempts:

3 left

💡 Hint

Common Mistakes

Including a case not requested like 'extraLarge'

Using uppercase letters

The enum Size includes the cases small, medium, and large as required.

Practice

1. What is the purpose of an enum in Swift?

easy

A. To group related values under one name

B. To create a function

C. To declare a variable

D. To write a loop

Solution

1. Step 1: Understand what enums represent

   Enums group related values together to make code clearer and safer.

2. Step 2: Compare options with enum purpose

   Only To group related values under one name correctly describes grouping related values under one name.

3. Final Answer:

   To group related values under one name -> Option A

4. Quick Check:

   Enum purpose = Group related values [OK]

Hint: Enums group related values clearly and safely [OK]

Common Mistakes:

• Confusing enums with functions
• Thinking enums declare variables
• Mixing enums with loops

2. Which of the following is the correct way to declare an enum named Direction with cases north, south, east, and west?

easy

A. enum Direction = { north, south, east, west }

B. enum Direction: north, south, east, west {}

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

D. enum Direction { north; south; east; west }

Solution

1. Step 1: Recall Swift enum syntax

   Enums use the keyword enum, followed by the name and curly braces containing case declarations separated by commas.

2. Step 2: Check each option's syntax

   enum Direction { case north, south, east, west } uses correct syntax: enum Direction { case north, south, east, west }. Others use invalid syntax.

3. Final Answer:

   enum Direction { case north, south, east, west } -> Option C

4. Quick Check:

   Correct enum syntax = enum Direction { case north, south, east, west } [OK]

Hint: Use 'case' keyword with comma-separated values inside braces [OK]

Common Mistakes:

• Using '=' instead of braces
• Omitting 'case' keyword
• Separating cases with semicolons

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

enum Light {
    case red, yellow, green
}

let current = Light.red
switch current {
case .red:
    print("Stop")
case .yellow:
    print("Caution")
case .green:
    print("Go")
}

medium

A. No output

B. Go

C. Caution

D. Stop

Solution

1. Step 1: Identify the enum case assigned

   The variable current is assigned Light.red.

2. Step 2: Match the switch case for current

   The switch matches .red and prints "Stop".

3. Final Answer:

   Stop -> Option D

4. Quick Check:

   Light.red triggers "Stop" output [OK]

Hint: Match enum case in switch to get output [OK]

Common Mistakes:

• Confusing enum cases with strings
• Forgetting dot prefix in switch
• Assuming default output

4. Identify the error in this enum declaration:

enum Weather {
    case sunny
    case rainy
    case windy
    case
}

medium

A. Missing case name after 'case' keyword

B. Enum name is invalid

C. Curly braces are missing

D. Enum cases should be strings

Solution

1. Step 1: Review each enum case line

   The last line has case without a case name, which is invalid syntax.

2. Step 2: Confirm other parts are correct

   Enum name and braces are correct; cases do not need to be strings.

3. Final Answer:

   Missing case name after 'case' keyword -> Option A

4. Quick Check:

   Every 'case' must have a name [OK]

Hint: Each 'case' must have a name after it [OK]

Common Mistakes:

• Leaving 'case' empty
• Thinking cases need quotes
• Missing braces around enum

5. You want to create an enum Planet with cases for mercury, venus, and earth. Then, write a function that returns a friendly message for each planet. Which code correctly implements this?

hard

A. enum Planet { mercury, venus, earth }
func message(planet: Planet) -> String {
if planet == mercury { return "Closest to the Sun" }
else if planet == venus { return "Second planet" }
else { return "Our home" }
}

B. enum Planet { case mercury, venus, earth }
func message(for planet: Planet) -> String {
switch planet {
case .mercury: return "Closest to the Sun"
case .venus: return "Second planet"
case .earth: return "Our home"
}
}

C. enum Planet { case mercury, venus, earth }
func message(planet: Planet) -> String {
if planet == mercury { return "Closest to the Sun" }
else if planet == venus { return "Second planet" }
else { return "Our home" }
}

D. enum Planet { case mercury, venus, earth }
func message(for planet: Planet) -> String {
switch planet {
case mercury: return "Closest to the Sun"
case venus: return "Second planet"
case earth: return "Our home"
}
}

Solution

1. Step 1: Check enum declaration syntax

   Options A, C, and D declare enum correctly with case keyword; B misses it, so B is invalid.

2. Step 2: Check function parameter and switch usage

   enum Planet { case mercury, venus, earth } func message(for planet: Planet) -> String { switch planet { case .mercury: return "Closest to the Sun" case .venus: return "Second planet" case .earth: return "Our home" } } uses switch with dot syntax for cases and correct function signature. enum Planet { case mercury, venus, earth } func message(planet: Planet) -> String { if planet == mercury { return "Closest to the Sun" } else if planet == venus { return "Second planet" } else { return "Our home" } } uses if-else without dot syntax (.mercury), causing compile error. enum Planet { case mercury, venus, earth } func message(for planet: Planet) -> String { switch planet { case mercury: return "Closest to the Sun" case venus: return "Second planet" case earth: return "Our home" } } misses dot prefix in switch cases, causing error.

3. Final Answer:

   enum Planet { case mercury, venus, earth } func message(for planet: Planet) -> String { switch planet { case .mercury: return "Closest to the Sun" case .venus: return "Second planet" case .earth: return "Our home" } } -> Option B

4. Quick Check:

   Enum with 'case' and switch with dot cases [OK]

Hint: Use 'case' keyword and dot prefix in switch cases [OK]

Common Mistakes:

• Omitting 'case' keyword in enum
• Missing dot prefix in switch cases
• Using if without dot prefix for enum cases