Why protocol-oriented design matters in Swift - See It in Action

Why protocol-oriented design matters

📖 Scenario: Imagine you are building a simple app to manage different types of vehicles. Each vehicle can start and stop, but they do these actions differently. You want a clean way to organize this behavior so you can add more vehicle types easily in the future.

🎯 Goal: You will create a protocol to define common vehicle actions, then make different vehicle types conform to this protocol. This shows why protocol-oriented design helps keep code simple and flexible.

📋 What You'll Learn

Create a protocol called Vehicle with two methods: start() and stop()

Create a struct called Car that conforms to Vehicle and implements start() and stop()

Create a struct called Bicycle that conforms to Vehicle and implements start() and stop()

Create an array called vehicles containing one Car and one Bicycle

Use a for loop to call start() and stop() on each vehicle in the vehicles array

Print messages inside each start() and stop() method to show which vehicle is starting or stopping

💡 Why This Matters

🌍 Real World

Protocol-oriented design is used in apps to organize code so different objects can share behavior without repeating code. For example, many types of vehicles or UI elements can follow the same protocol to simplify how the app controls them.

💼 Career

Understanding protocol-oriented design is important for Swift developers because it helps write clean, reusable, and flexible code. Many iOS apps and frameworks use protocols to manage complex behaviors in a simple way.

1

Create the Vehicle protocol

Create a protocol called Vehicle with two methods: start() and stop().

Swift

// Create the Vehicle protocol with start() and stop() methods
// Your code here

Need a hint?

Protocols define a blueprint of methods. Use protocol Vehicle {} and add func start() and func stop() inside.

2

Create Car and Bicycle structs conforming to Vehicle

Create a struct called Car that conforms to Vehicle and implements start() and stop() methods. Then create a struct called Bicycle that also conforms to Vehicle and implements start() and stop() methods.

Swift

protocol Vehicle {
    func start()
    func stop()
}

// Create struct Car conforming to Vehicle
// Create struct Bicycle conforming to Vehicle
// Your code here

Need a hint?

Use struct Car: Vehicle {} and inside add func start() and func stop() with print statements. Do the same for Bicycle.

3

Create an array of vehicles

Create an array called vehicles containing one Car() and one Bicycle().

Swift

protocol Vehicle {
    func start()
    func stop()
}

struct Car: Vehicle {
    func start() {
        print("Car is starting")
    }
    func stop() {
        print("Car is stopping")
    }
}

struct Bicycle: Vehicle {
    func start() {
        print("Bicycle is starting")
    }
    func stop() {
        print("Bicycle is stopping")
    }
}

// Create an array called vehicles with Car() and Bicycle()
// Your code here

Need a hint?

Use let vehicles: [Vehicle] = [Car(), Bicycle()] to create the array.

4

Use a loop to start and stop all vehicles

Use a for loop with variable vehicle to iterate over vehicles. Inside the loop, call vehicle.start() and vehicle.stop(). Print the output.

Swift

protocol Vehicle {
    func start()
    func stop()
}

struct Car: Vehicle {
    func start() {
        print("Car is starting")
    }
    func stop() {
        print("Car is stopping")
    }
}

struct Bicycle: Vehicle {
    func start() {
        print("Bicycle is starting")
    }
    func stop() {
        print("Bicycle is stopping")
    }
}

let vehicles: [Vehicle] = [Car(), Bicycle()]

// Use a for loop to call start() and stop() on each vehicle
// Your code here

Need a hint?

Use for vehicle in vehicles { vehicle.start(); vehicle.stop() } to run the methods on each vehicle.