Raw values for enums in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an enum with raw values of type String.

Swift

enum Direction: String {
    case north = [1]
    case south = "South"
}

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

A"North"

BNorth

C'North'

Dnorth

Attempts:

3 left

💡 Hint

Common Mistakes

Using unquoted identifiers as raw values.

Using single quotes instead of double quotes for strings.

The raw value for the case must be a String literal, so it needs to be in double quotes.

2fill in blank

medium

Complete the code to declare an enum with raw values of type Int starting at 1.

Swift

enum Weekday: Int {
    case monday = [1]
    case tuesday
}

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

A"1"

B1

C0

Dmonday

Attempts:

3 left

💡 Hint

Common Mistakes

Using string "1" instead of integer 1.

Starting raw values at 0 when 1 is required.

Raw values of type Int must be integers. To start at 1, assign monday = 1.

3fill in blank

hard

Fix the error in the enum raw value declaration.

Swift

enum Color: String {
    case red = [1]
    case blue = "Blue"
}

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

Ared

BRed

C'Red'

D"Red"

Attempts:

3 left

💡 Hint

Common Mistakes

Using single quotes instead of double quotes.

Using unquoted identifiers as raw values.

Raw values of type String must be enclosed in double quotes. Using "Red" is correct.

4fill in blank

hard

Fill both blanks to create an enum with raw values and access a raw value.

Swift

enum Planet: Int {
    case earth = [1]
    case mars = [2]
}
let marsValue = Planet.mars.rawValue

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

A3

B2

C4

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using string literals instead of integers.

Assigning the same raw value to both cases.

Assign earth = 2 and mars = 3 to set raw values correctly.

5fill in blank

hard

Fill all three blanks to create an enum with raw values and a function returning a raw value.

Swift

enum Status: String {
    case success = [1]
    case failure = [2]
    case unknown = [3]
}

func getStatusMessage(_ status: Status) -> String {
    return status.rawValue
}

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

A"Success"

B"Failure"

C"Unknown"

D"Error"

Attempts:

3 left

💡 Hint

Common Mistakes

Using unquoted strings or single quotes.

Assigning incorrect raw values that don't match the case.

Each case must have a string raw value in double quotes matching the case meaning.

Practice

1. What is the purpose of raw values in Swift enums?

easy

A. To allow enums to inherit from classes

B. To assign fixed simple values like strings or numbers to enum cases

C. To make enums mutable after declaration

D. To create functions inside enums

Solution

1. Step 1: Understand what raw values are

   Raw values are fixed values assigned to enum cases, like strings or numbers.

2. Step 2: Identify the purpose of raw values

   They help convert enum cases to simple data types for saving or displaying.

3. Final Answer:

   To assign fixed simple values like strings or numbers to enum cases -> Option B

4. Quick Check:

   Raw values = fixed simple values [OK]

Hint: Raw values give enums fixed simple data like strings or numbers [OK]

Common Mistakes:

• Thinking raw values make enums mutable
• Confusing raw values with associated values
• Believing enums can inherit from classes

2. Which of the following is the correct syntax to declare an enum with raw values in Swift?

easy

A. enum Direction: Int { case north; case south }

B. enum Direction { case north = "N" case south = "S" }

C. enum Direction: String { case north = "N" case south = "S" }

D. enum Direction: String { north = "N", south = "S" }

Solution

1. Step 1: Check enum declaration with raw values

   Raw values require specifying the type after enum name, e.g., : String.

2. Step 2: Verify correct case syntax

   Cases use 'case name = value' syntax, separated by new lines or semicolons.

3. Final Answer:

   enum Direction: String { case north = "N" case south = "S" } -> Option C

4. Quick Check:

   Raw value enum syntax = enum Direction: String { case north = "N" case south = "S" } [OK]

Hint: Raw value enums need type after name and '=' for values [OK]

Common Mistakes:

• Omitting the raw value type after enum name
• Using commas instead of separate case lines
• Assigning raw values without specifying type

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

enum Weekday: Int {
    case monday = 1
    case tuesday
    case wednesday
}
print(Weekday.tuesday.rawValue)

medium

A. 1

B. Error: rawValue not found

C. 3

D. 2

Solution

1. Step 1: Understand raw value auto-increment

   When the first case has a raw value (1), following cases auto-increment by 1.

2. Step 2: Identify raw value of 'tuesday'

   Since monday = 1, tuesday = 2, wednesday = 3.

3. Final Answer:

   2 -> Option D

4. Quick Check:

   Auto-increment raw values = 2 [OK]

Hint: Raw Int values auto-increment from first assigned value [OK]

Common Mistakes:

• Assuming all raw values must be explicitly assigned
• Confusing rawValue with case index
• Expecting an error when accessing rawValue

4. Identify the error in this enum declaration:

enum Color: String {
    case red = 1
    case green = "Green"
    case blue = "Blue"
}

medium

A. Raw values must all be of the declared type String

B. Enum cases cannot have raw values

C. Raw values must be integers only

D. Missing semicolon after each case

Solution

1. Step 1: Check raw value type consistency

   The enum declares raw type String, so all raw values must be strings.

2. Step 2: Identify the incorrect raw value

   Case 'red' has raw value 1 (an Int), which conflicts with String type.

3. Final Answer:

   Raw values must all be of the declared type String -> Option A

4. Quick Check:

   Raw values must match enum type [OK]

Hint: All raw values must match enum's declared raw type [OK]

Common Mistakes:

• Mixing raw value types in one enum
• Thinking semicolons are required after cases
• Believing enums can't have raw values

5. Given this enum:

enum StatusCode: Int {
    case success = 200
    case notFound = 404
    case serverError = 500
}

func message(for code: Int) -> String {
    if let status = StatusCode(rawValue: code) {
        switch status {
        case .success: return "OK"
        case .notFound: return "Not Found"
        case .serverError: return "Server Error"
        }
    } else {
        return "Unknown"
    }
}

print(message(for: 404))
print(message(for: 201))

What is the output?

hard

A. Not Found
Unknown

B. OK
Unknown

C. Not Found
Server Error

D. Error at runtime

Solution

1. Step 1: Understand rawValue initializer

   StatusCode(rawValue: 404) returns .notFound; 201 returns nil.

2. Step 2: Trace function output for each input

   For 404, returns "Not Found"; for 201, returns "Unknown".

3. Final Answer:

   Not Found Unknown -> Option A

4. Quick Check:

   Raw value init maps code to enum or nil [OK]

Hint: Raw value init returns nil if no matching case [OK]

Common Mistakes:

• Assuming rawValue init always returns a case
• Confusing rawValue with case index
• Expecting runtime error for unknown raw value