Enum with switch pattern matching in Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of switch with enum and associated values

What is the output of this Swift code using enum and switch pattern matching?

Swift

enum Device {
    case iPhone(model: String)
    case iPad(model: String)
    case mac
}

let myDevice = Device.iPhone(model: "13 Pro")

switch myDevice {
case .iPhone(let model):
    print("iPhone model: \(model)")
case .iPad(let model):
    print("iPad model: \(model)")
case .mac:
    print("Mac computer")
}

A iPhone model: 13 Pro

B Mac computer

C iPad model: 13 Pro

D Compilation error

💡 Hint

Look at the enum case and the associated value passed to it.

The variable myDevice is assigned the enum case iPhone with model "13 Pro". The switch matches .iPhone and prints the model.

❓ Predict Output

intermediate

Switch pattern matching with multiple associated values

What will this Swift code print when run?

Swift

enum Result {
    case success(code: Int, message: String)
    case failure(error: String)
}

let response = Result.success(code: 200, message: "OK")

switch response {
case .success(let code, let message) where code == 200:
    print("Success with code 200: \(message)")
case .success(let code, let message):
    print("Success with code \(code): \(message)")
case .failure(let error):
    print("Failure: \(error)")
}

A Compilation error

B Success with code 200: OK

C Failure: OK

D Success with code 200: failure

💡 Hint

Check the where clause in the first case of the switch.

The response matches the first case because code is 200, so it prints the message with that case.

🔧 Debug

advanced

Identify the error in switch pattern matching with enum

What error does this Swift code produce when compiled?

Swift

enum Status {
    case ready
    case loading(progress: Int)
    case error(message: String)
}

let currentStatus = Status.loading(progress: 50)

switch currentStatus {
case .ready:
    print("Ready")
case .loading:
    print("Loading")
case .error(let message):
    print("Error: \(message)")
}

A Runtime error: Unexpected nil value

B No error, prints: Loading

C Error: Enum case 'loading' not handled correctly

D Error: Missing associated value pattern in case .loading

💡 Hint

Check how the .loading case is matched in the switch.

The .loading case has an associated value but the switch case does not bind or ignore it, causing a compile error.

🧠 Conceptual

advanced

Understanding exhaustive switch with enums

Why does Swift require the switch statement to be exhaustive when switching over enums?

A To force the programmer to use if-else instead of switch

B Because Swift does not support default cases in switch statements

C To ensure all possible enum cases are handled, preventing runtime errors

D Because enums can only have one case

💡 Hint

Think about safety and completeness in code.

Swift requires exhaustive switches to make sure all enum cases are handled, avoiding unexpected behavior at runtime.

❓ Predict Output

expert

Output of nested enum with switch pattern matching

What is the output of this Swift code with nested enums and switch pattern matching?

Swift

enum Network {
    enum Response {
        case success(data: String)
        case failure(code: Int)
    }
    case request(url: String, response: Response)
}

let netCall = Network.request(url: "example.com", response: .failure(code: 404))

switch netCall {
case .request(let url, let response):
    switch response {
    case .success(let data):
        print("Success from \(url): \(data)")
    case .failure(let code) where code >= 400:
        print("Error \(code) from \(url)")
    default:
        print("Other response from \(url)")
    }
}

A Error 404 from example.com

B Success from example.com: failure

C Other response from example.com

D Compilation error

💡 Hint

Look at the nested switch and the where clause condition.

The outer switch matches .request and extracts url and response. The inner switch matches .failure with code 404 which is >= 400, so it prints the error message.