Data types (Int, Double, String, Bool) in iOS Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

📝 Syntax

intermediate

Swift Data Type Declaration

What is the output of this Swift code snippet?

iOS Swift

let number: Int = 10
let price: Double = 9.99
let name: String = "Coffee"
let isAvailable: Bool = true
print("\(name) costs \(price) and availability is \(isAvailable)")

A Coffee costs 9.99 and availability is True

B Coffee costs 9.99 and availability is 1

C Coffee costs 9.99 and availability is true

D Coffee costs 9.99 and availability is Yes

💡 Hint

Remember how Swift prints Boolean values in strings.

In Swift, Bool values print as 'true' or 'false' in lowercase when interpolated in strings.

❓ ui_behavior

intermediate

Displaying Different Data Types in UILabel

You want to show an integer, a double, and a boolean in a UILabel in Swift. Which code snippet correctly converts all values to a string for display?

A label.text = "Int: " + String(intValue) + ", Double: " + String(doubleValue) + ", Bool: " + String(boolValue)

B label.text = String(intValue) + String(doubleValue) + String(boolValue)

C label.text = "Int: \(intValue), Double: \(doubleValue), Bool: \(boolValue)"

D label.text = "Int: " + intValue + ", Double: " + doubleValue + ", Bool: " + boolValue

💡 Hint

You cannot add non-string types directly to strings in Swift.

In Swift, you must convert non-string types to String before concatenation with + operator. String interpolation (option A) also works but option A explicitly converts each value.

🧠 Conceptual

advanced

Type Safety in Swift

Which statement best describes Swift's type safety with Int, Double, String, and Bool?

A Swift automatically converts String to Int if the string contains digits.

B Swift requires explicit conversion between Int and Double to avoid type errors.

C Swift treats Bool as a subtype of Int, so they can be used interchangeably.

D Swift allows implicit conversion between Int and Double without errors.

💡 Hint

Think about how Swift handles different numeric types.

Swift is strongly typed and does not allow implicit conversion between Int and Double. You must convert explicitly using initializers like Double(intValue).

❓ lifecycle

advanced

Variable Initialization and Default Values

What is the default value of an uninitialized variable of type Bool in Swift?

A true

B false

C nil

D Swift does not allow uninitialized variables; it causes a compile error

💡 Hint

Swift enforces initialization before use.

Swift requires all variables to be initialized before use. Declaring a variable without initialization causes a compile-time error.

🔧 Debug

expert

Debugging Type Mismatch Error

What error will this Swift code produce? let value: Int = 5 let result: Double = value print(result)

iOS Swift

let value: Int = 5
let result: Double = value
print(result)

A Type mismatch error: Cannot assign Int to Double without conversion

B Prints 5.0 without error

C Runtime error: Cannot convert Int to Double

D Syntax error: Missing semicolon

💡 Hint

Check how Swift handles assigning Int to Double variables.

Swift does not implicitly convert Int to Double. You must explicitly convert using Double(value).