Type constraints with protocol conformance in Swift - Mini Project: Build & Apply

Type constraints with protocol conformance

📖 Scenario: You are building a simple system to handle different shapes and calculate their areas. Each shape must follow a common rule to provide its area.

🎯 Goal: Create a protocol called Shape with a property for area. Then, create two structs that conform to this protocol. Finally, write a generic function that only accepts types conforming to Shape and prints their area.

📋 What You'll Learn

Create a protocol named Shape with a read-only property area of type Double

Create a struct Square that conforms to Shape with a sideLength property

Create a struct Circle that conforms to Shape with a radius property

Write a generic function printArea that accepts a parameter constrained to Shape and prints its area

💡 Why This Matters

🌍 Real World

Protocols and type constraints help write flexible and reusable code that works with many types sharing common behavior.

💼 Career

Understanding protocol conformance and generics is essential for Swift developers building scalable and maintainable apps.

1

Create the Shape protocol

Create a protocol called Shape with a read-only property area of type Double.

Swift

# Your code here

Need a hint?

Protocols define a blueprint. Use var area: Double { get } to declare a read-only property.

2

Create Square and Circle structs conforming to Shape

Create a struct called Square with a sideLength property of type Double. Make it conform to Shape by implementing the area property as sideLength squared. Also, create a struct called Circle with a radius property of type Double. Make it conform to Shape by implementing the area property as π times radius squared.

Swift

protocol Shape {
    var area: Double { get }
}

# Your code here

Need a hint?

Use struct Name: Shape to conform. Calculate area inside a computed property.

3

Write a generic function with type constraint

Write a generic function called printArea that accepts one parameter named shape of generic type T. Add a type constraint so that T must conform to the Shape protocol. Inside the function, print the area of the shape using print("Area: \(shape.area)").

Swift

protocol Shape {
    var area: Double { get }
}

struct Square: Shape {
    var sideLength: Double
    var area: Double {
        sideLength * sideLength
    }
}

struct Circle: Shape {
    var radius: Double
    var area: Double {
        Double.pi * radius * radius
    }
}

# Your code here

Need a hint?

Use func printArea<T: Shape>(shape: T) to add the type constraint.

4

Call printArea with Square and Circle instances

Create a constant square of type Square with sideLength 4.0. Create a constant circle of type Circle with radius 3.0. Call printArea with square and then with circle.

Swift

protocol Shape {
    var area: Double { get }
}

struct Square: Shape {
    var sideLength: Double
    var area: Double {
        sideLength * sideLength
    }
}

struct Circle: Shape {
    var radius: Double
    var area: Double {
        Double.pi * radius * radius
    }
}

func printArea(shape: T) {
    print("Area: \(shape.area)")
}

# Your code here

Need a hint?

Create instances with the exact property values and call printArea with them.