Associated values per case in Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of enum with associated values

What is the output of this Swift code?

Swift

enum Result {
    case success(data: String)
    case failure(errorCode: Int)
}

let response = Result.success(data: "File loaded")
switch response {
case .success(let data):
    print("Success: \(data)")
case .failure(let code):
    print("Error code: \(code)")
}

A Compilation error

B Error code: 0

C Success: data

D Success: File loaded

💡 Hint

Look at which case is assigned to the variable and what the associated value is.

The enum instance is created with the success case and the associated value "File loaded". The switch matches .success and prints the associated data.

❓ Predict Output

intermediate

Extracting multiple associated values

What will this Swift code print?

Swift

enum Shape {
    case rectangle(width: Int, height: Int)
    case circle(radius: Int)
}

let shape = Shape.rectangle(width: 5, height: 10)
switch shape {
case .rectangle(let w, let h):
    print("Area: \(w * h)")
case .circle(let r):
    print("Area: \(3.14 * Double(r * r))")
}

A Area: 50

B Area: 15

C Area: 78.5

D Runtime error

💡 Hint

Calculate the area of the rectangle using width and height.

The shape is a rectangle with width 5 and height 10, so area is 5 * 10 = 50.

🔧 Debug

advanced

Identify the error with associated values

What error does this Swift code produce?

Swift

enum Device {
    case phone(model: String)
    case tablet
}

let myDevice = Device.phone(model: "iPhone 14")
switch myDevice {
case .phone:
    print("Phone detected")
case .tablet:
    print("Tablet detected")
}

A No error, prints 'Phone detected'

B Error: Missing default case in switch

C Error: Associated value 'model' not extracted in case pattern

D Runtime crash due to missing associated value

💡 Hint

Check if the associated value is handled in the switch case pattern.

The case .phone has an associated value 'model' but the switch case pattern does not extract it, causing a compiler error.

🧠 Conceptual

advanced

Understanding associated values in enums

Which statement about Swift enums with associated values is true?

A All cases must have the same associated value types.

B Each case can store different types and amounts of associated values.

C Associated values must be constants and cannot be extracted.

D Enums with associated values cannot be used in switch statements.

💡 Hint

Think about flexibility of enum cases with associated values.

Swift enums allow each case to have zero or more associated values of any type, and these can differ between cases.

❓ Predict Output

expert

Output of nested associated values in enum

What is the output of this Swift code?

Swift

enum Response {
    case success(data: (id: Int, message: String))
    case failure(error: String)
}

let result = Response.success(data: (id: 101, message: "OK"))
switch result {
case .success(let data):
    print("ID: \(data.id), Message: \(data.message)")
case .failure(let error):
    print("Error: \(error)")
}

A ID: 101, Message: OK

B Error: OK

C ID: (101, "OK"), Message: nil

D Compilation error due to tuple usage

💡 Hint

Look at how the tuple is used as an associated value and accessed.

The success case has a tuple with named elements. The switch extracts the tuple and prints its fields.