Enum methods and computed properties in Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of enum method with computed property

What is the output of this Swift code?

Swift

enum Direction {
    case north, south, east, west
    
    var isVertical: Bool {
        return self == .north || self == .south
    }
    
    func description() -> String {
        return isVertical ? "Vertical" : "Horizontal"
    }
}

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

A "Vertical"

B "north"

C Compilation error

D "Horizontal"

💡 Hint

Check how the computed property 'isVertical' is defined and used in the method.

The enum Direction has a computed property 'isVertical' that returns true only for .north and .south. Since 'dir' is .east, 'isVertical' is false, so description() returns "Horizontal".

❓ Predict Output

intermediate

Computed property with associated values

What will be printed by this Swift code?

Swift

enum Result {
    case success(Int)
    case failure(String)
    
    var message: String {
        switch self {
        case .success(let code):
            return "Success with code \(code)"
        case .failure(let error):
            return "Failed: \(error)"
        }
    }
}

let res = Result.failure("Network error")
print(res.message)

A "Failed: Network error"

B "Success with code 0"

C Runtime error

D "Failed: nil"

💡 Hint

Look at how the associated value is extracted in the computed property.

The enum case is .failure with associated value "Network error", so the computed property returns "Failed: Network error".

🔧 Debug

advanced

Identify the error in enum method

What error does this Swift code produce when compiled?

Swift

enum Status {
    case ready, waiting
    
    func isReady() -> Bool {
        switch self {
        case .ready:
            return true
        case .waiting
            return false
        }
    }
}

A Runtime error: Missing return statement

B TypeError: Cannot return Bool from function

C SyntaxError: Missing colon after 'case .waiting'

D No error, compiles fine

💡 Hint

Check the switch case syntax carefully.

The case '.waiting' is missing a colon ':' after it, causing a syntax error.

❓ Predict Output

advanced

Computed property returning different types

What is the output of this Swift code?

Swift

enum Measurement {
    case weight(Double)
    case count(Int)
    
    var description: String {
        switch self {
        case .weight(let w):
            return "Weight: \(w) kg"
        case .count(let c):
            return "Count: \(c) items"
        }
    }
}

let m = Measurement.weight(3.5)
print(m.description)

A Compilation error: mismatched types

B "Weight: 3.5 kg"

C "Count: 3.5 items"

D "Weight: 3 kg"

💡 Hint

Check the associated value type and string interpolation.

The enum case is .weight with value 3.5, so the description returns "Weight: 3.5 kg".

🧠 Conceptual

expert

Why use computed properties in enums?

Which of the following best explains why computed properties are useful in Swift enums?

A They enable adding dynamic behavior or derived values based on the enum case and its associated values.

B They allow storing additional data inside enum cases without associated values.

C They make enums mutable so their cases can change at runtime.

D They automatically generate raw values for enum cases.

💡 Hint

Think about what computed properties do in general.

Computed properties let you add dynamic behavior or calculate values based on the enum case and its associated data, without storing extra data.