Extending built-in types in Swift - Mini Project: Build & Apply

Extending built-in types

📖 Scenario: Imagine you want to add a new feature to Swift's built-in Int type. You want to check if a number is even or odd easily, just like calling a simple property.

🎯 Goal: You will create an extension to the Int type that adds a computed property called isEven. This property will return true if the number is even, and false if it is odd.

📋 What You'll Learn

Create an extension for the built-in Int type

Add a computed property called isEven that returns a Bool

Use the modulo operator (%) to determine if a number is even

Test the new property with a few example numbers

Print the results to the console

💡 Why This Matters

🌍 Real World

Extending built-in types lets you add useful features to existing data types without changing their original code. This helps keep your code clean and reusable.

💼 Career

Many Swift developers extend built-in types to add custom behavior, making their apps more expressive and easier to maintain.

1

Create an integer variable

Create a variable called number and set it to the integer 10.

Swift

# Create a variable called number and set it to 10
# Your code here

Need a hint?

Use var number = 10 to create the variable.

2

Create an extension for Int

Create an extension for the built-in Int type. Inside it, add a computed property called isEven that returns a Bool. For now, just return false inside the property.

Swift

var number = 10

// Create an extension for Int with a computed property isEven
// Your code here

Need a hint?

Use extension Int { var isEven: Bool { return false } } to create the extension and property.

3

Implement the isEven logic

Change the isEven computed property to return true if the number is even, and false if it is odd. Use the modulo operator % to check if self % 2 == 0.

Swift

var number = 10

extension Int {
    var isEven: Bool {
        // Return true if self is even, false otherwise
        // Your code here
    }
}

Need a hint?

Use return self % 2 == 0 inside the computed property.

4

Test and print the result

Use print to display the result of number.isEven. This will show true if number is even, or false if odd.

Swift

var number = 10

extension Int {
    var isEven: Bool {
        return self % 2 == 0
    }
}

// Print whether number is even
# Your code here

Need a hint?

Use print(number.isEven) to show the result.