Protocol extensions with default implementations in Swift - Mini Project: Build & Apply

Protocol extensions with default implementations

📖 Scenario: Imagine you are building a simple app that manages different types of vehicles. Each vehicle can describe itself with a message. You want to make it easy to add new vehicle types without rewriting common code.

🎯 Goal: You will create a protocol called Vehicle with a method to describe the vehicle. Then, you will add a protocol extension that provides a default description. Finally, you will create specific vehicle types that use the default description or provide their own.

📋 What You'll Learn

Create a protocol named Vehicle with a method func description() -> String

Add a protocol extension for Vehicle that provides a default implementation of description()

Create a struct Car that conforms to Vehicle and uses the default description

Create a struct Bicycle that conforms to Vehicle and provides its own description() implementation

Print the descriptions of both Car and Bicycle instances

💡 Why This Matters

🌍 Real World

Protocol extensions with default implementations let you write flexible and reusable code. For example, apps that manage many types of objects can share common behavior easily.

💼 Career

Understanding protocol extensions is important for Swift developers. It helps in writing clean, maintainable code and is widely used in iOS app development.

1

Create the Vehicle protocol

Create a protocol called Vehicle with a method func description() -> String.

Swift

# Create the Vehicle protocol with func description() -> String
# Your code here

Need a hint?

Use the protocol keyword and declare the method signature without a body.

2

Add a default implementation with a protocol extension

Add a protocol extension for Vehicle that provides a default implementation of description() returning the string "This is a vehicle.".

Swift

protocol Vehicle {
    func description() -> String
}

// Add a protocol extension for Vehicle with default description() implementation
# Your code here

Need a hint?

Use extension Vehicle and implement description() with the return string.

3

Create Car and Bicycle structs conforming to Vehicle

Create a struct called Car that conforms to Vehicle and uses the default description(). Then create a struct called Bicycle that conforms to Vehicle and provides its own description() returning "This is a bicycle.".

Swift

protocol Vehicle {
    func description() -> String
}

extension Vehicle {
    func description() -> String {
        return "This is a vehicle."
    }
}

// Create struct Car conforming to Vehicle
// Create struct Bicycle conforming to Vehicle with its own description()
# Your code here

Need a hint?

Define Car without adding description() to use the default. Define Bicycle with its own description() method.

4

Print descriptions of Car and Bicycle

Create instances of Car and Bicycle. Then print the result of calling description() on each instance.

Swift

protocol Vehicle {
    func description() -> String
}

extension Vehicle {
    func description() -> String {
        return "This is a vehicle."
    }
}

struct Car: Vehicle {
    // Uses default description()
}

struct Bicycle: Vehicle {
    func description() -> String {
        return "This is a bicycle."
    }
}

// Create instances of Car and Bicycle
// Print their descriptions
# Your code here

Need a hint?

Create variables myCar and myBike for the instances. Use print() to show their descriptions.