Type conversion is always explicit in Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of explicit type conversion in Swift

What is the output of this Swift code snippet?

Swift

let intVal: Int = 10
let doubleVal: Double = 3.5
let result = Double(intVal) + doubleVal
print(result)

A 13.5

B 13

C Type error at compile time

D 10.0

💡 Hint

Remember that Swift requires explicit conversion between Int and Double types.

The integer 10 is explicitly converted to Double before addition, so 10.0 + 3.5 equals 13.5.

❓ Predict Output

intermediate

Result of forced type conversion with optional

What will be printed by this Swift code?

Swift

let str = "123"
let num = Int(str)!
print(num + 1)

A 124

B 1231

C Type error at compile time

D Runtime error: nil unwrapping

💡 Hint

The string contains only digits, so conversion to Int succeeds.

Int(str) converts the string "123" to integer 123. Forced unwrapping (!) succeeds, so 123 + 1 equals 124.

❓ Predict Output

advanced

What error occurs with implicit conversion?

What error does this Swift code produce?

Swift

let a: Int = 5
let b: Double = 2.0
let c = a + b
print(c)

A 7.0

B Type error: binary operator '+' cannot be applied to operands of type 'Int' and 'Double'

C 5 + 2 = 7

D Runtime error: cannot add Int and Double

💡 Hint

Swift does not allow implicit conversion between Int and Double in arithmetic operations.

Swift requires explicit conversion; adding Int and Double without conversion causes a compile-time type error.

❓ Predict Output

advanced

Output of converting Double to Int explicitly

What is the output of this Swift code?

Swift

let pi: Double = 3.99
let intPi = Int(pi)
print(intPi)

A 4

B Type error at compile time

C 3.99

D 3

💡 Hint

Converting Double to Int truncates the decimal part.

Int(pi) truncates the decimal part, so 3.99 becomes 3.

🧠 Conceptual

expert

Why is explicit type conversion required in Swift?

Which of the following best explains why Swift requires explicit type conversion between numeric types?

A To improve runtime performance by avoiding automatic conversions

B Because Swift does not support numeric operations between different types

C To prevent unexpected data loss or bugs by making conversions clear and intentional

D Because implicit conversions are handled automatically by the compiler

💡 Hint

Think about safety and clarity in code.

Explicit conversions make the programmer aware of possible data loss or changes, preventing subtle bugs.