Explicit type annotation in Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Swift code with explicit type annotation?

Consider the following Swift code snippet. What will be printed?

Swift

let number: Int = 5
let result = number * 2
print(result)

A Compilation error

B 5

C 10

D Type error

💡 Hint

Look at the type of number and the operation performed.

The variable number is explicitly declared as an Int. Multiplying it by 2 results in 10, which is printed.

❓ Predict Output

intermediate

What is the type of variable value here?

Given the code below, what is the type of value?

Swift

let value: Double = 3.14
print(type(of: value))

A Int

B Double

C Float

D String

💡 Hint

Check the explicit type annotation used when declaring value.

The variable value is explicitly declared as Double, so its type is Double.

🔧 Debug

advanced

Why does this Swift code cause a compilation error?

Examine the code below. Why does it fail to compile?

Swift

let text: Int = "Hello"
print(text)

A Cannot assign a String to an Int variable

B Missing semicolon at the end of the line

C Variable <code>text</code> is not initialized

D Print statement syntax is incorrect

💡 Hint

Look at the type annotation and the assigned value.

The variable text is declared as Int but assigned a String. This causes a type mismatch error.

❓ Predict Output

advanced

What is the output of this Swift code with explicit type annotation and optional?

What will this code print?

Swift

let optionalNumber: Int? = 10
if let number: Int = optionalNumber {
    print(number * 3)
} else {
    print("No value")
}

A 30

B No value

C Optional(30)

D Compilation error

💡 Hint

Check how optional binding with explicit type annotation works.

The optional optionalNumber contains 10, so number is assigned 10 and multiplied by 3, printing 30.

🧠 Conceptual

expert

Why is explicit type annotation useful in Swift?

Choose the best reason why explicit type annotation is important in Swift programming.

A It automatically converts all types to String

B It makes the code run faster at runtime

C It allows variables to change types dynamically

D It helps the compiler catch type errors early and improves code readability

💡 Hint

Think about how Swift uses types to prevent bugs.

Explicit type annotation helps the compiler detect type mismatches early and makes the code clearer for humans reading it.