Raw values for enums in Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of enum raw value access

What is the output of this Swift code snippet?

Swift

enum Direction: String {
    case north = "N"
    case south = "S"
    case east = "E"
    case west = "W"
}

let dir = Direction.east
print(dir.rawValue)

A Direction.east

B "east"

C "E"

D "East"

💡 Hint

Check the raw value assigned to the case east.

The enum Direction has raw values of type String. The case east is assigned the raw value "E". Accessing dir.rawValue prints "E".

❓ Predict Output

intermediate

Raw value default assignment for Int enums

What will be printed by this Swift code?

Swift

enum Weekday: Int {
    case monday = 1
    case tuesday
    case wednesday
}

print(Weekday.tuesday.rawValue)

A 3

B 1

C tuesday

D 2

💡 Hint

Int raw values auto-increment from the first assigned value.

Since monday is assigned 1, tuesday gets 2 automatically, so printing rawValue of tuesday outputs 2.

❓ Predict Output

advanced

Using rawValue initializer with valid and invalid values

What is the output of this Swift code?

Swift

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

if let status = StatusCode(rawValue: 404) {
    print("Found: \(status)")
} else {
    print("Not found")
}

if let status = StatusCode(rawValue: 201) {
    print("Found: \(status)")
} else {
    print("Not found")
}

A

Found: notFound
Not found

B

Found: notFound
Found: 201

C

Not found
Not found

D

Found: 404
Not found

💡 Hint

rawValue initializer returns nil if no matching case exists.

StatusCode(rawValue: 404) matches notFound case, so prints Found: notFound. 201 does not match any case, so prints Not found.

❓ Predict Output

advanced

Raw values with mixed types in enum

What error or output does this Swift code produce?

Swift

enum MixedRaw: RawRepresentable {
    case intCase(Int)
    case stringCase(String)

    var rawValue: Any {
        switch self {
        case .intCase(let value): return value
        case .stringCase(let value): return value
        }
    }

    init?(rawValue: Any) {
        if let intValue = rawValue as? Int {
            self = .intCase(intValue)
        } else if let stringValue = rawValue as? String {
            self = .stringCase(stringValue)
        } else {
            return nil
        }
    }
}

let a = MixedRaw(rawValue: 10)
print(a?.rawValue ?? "nil")

A nil

B Compile-time error: enums cannot have associated values and raw values

C 10

D Runtime error

💡 Hint

Swift enums with associated values cannot have raw values.

Swift does not allow enums with associated values to have raw values. This code will not compile.

🧠 Conceptual

expert

Raw value uniqueness enforcement

What happens if you define a Swift enum with duplicate raw values like this?

Swift

enum Color: String {
    case red = "R"
    case green = "G"
    case blue = "R"
}

A Compile-time error due to duplicate raw values

B Compiles successfully, last case overwrites previous raw value

C Runtime error when accessing rawValue

D Compiles but rawValue of blue is nil

💡 Hint

Raw values must be unique in Swift enums.

Swift requires raw values to be unique. Duplicate raw values cause a compile-time error.

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