Adding computed properties in Swift - Mini Project: Build & Apply

Adding computed properties

📖 Scenario: You are creating a simple app to manage rectangles. Each rectangle has a width and height. You want to add a property that calculates the area automatically.

🎯 Goal: Build a Swift struct called Rectangle with stored properties for width and height, and add a computed property called area that calculates the rectangle's area.

📋 What You'll Learn

Create a struct named Rectangle with two stored properties: width and height of type Double.

Add a computed property called area that returns the product of width and height.

Create an instance of Rectangle with width 5.0 and height 3.0.

Print the value of the area property.

💡 Why This Matters

🌍 Real World

Computed properties help keep data consistent and avoid manual calculations in apps that manage shapes, sizes, or any related data.

💼 Career

Understanding computed properties is essential for Swift developers building iOS apps, as it helps write clean, efficient, and maintainable code.

1

Create the Rectangle struct with width and height

Create a Swift struct called Rectangle with two stored properties: width and height, both of type Double. Do not add any methods or computed properties yet.

Swift

struct Rectangle {
    // Your code here
}

Need a hint?

Use struct Rectangle { var width: Double; var height: Double } to define the shape.

2

Add a computed property for area

Inside the Rectangle struct, add a computed property called area of type Double that returns the product of width and height. Use the var area: Double { ... } syntax.

Swift

struct Rectangle {
    var width: Double
    var height: Double
    // Add computed property area here
}

Need a hint?

Computed properties use var area: Double { return width * height }.

3

Create a Rectangle instance

Create a constant called myRect and assign it a new Rectangle instance with width 5.0 and height 3.0.

Swift

struct Rectangle {
    var width: Double
    var height: Double
    var area: Double {
        return width * height
    }
}

// Create myRect instance here

Need a hint?

Use let myRect = Rectangle(width: 5.0, height: 3.0) to create the instance.

4

Print the area of the rectangle

Write a print statement to display the value of myRect.area.

Swift

struct Rectangle {
    var width: Double
    var height: Double
    var area: Double {
        return width * height
    }
}

let myRect = Rectangle(width: 5.0, height: 3.0)

// Print the area here

Need a hint?

Use print(myRect.area) to show the area.