Factory pattern with companion objects in Kotlin - Mini Project: Build & Apply

Factory pattern with companion objects

📖 Scenario: You are building a simple app that creates different types of vehicles. Each vehicle has a name and a type. You want to use the factory pattern with companion objects to create vehicles easily.

🎯 Goal: Build a Kotlin program that uses a companion object as a factory to create Vehicle objects with different types.

📋 What You'll Learn

Create a Vehicle class with name and type properties

Add a companion object inside Vehicle with a factory method create

The factory method should take name and type as parameters and return a Vehicle object

Use the factory method to create a vehicle

Print the vehicle's details

💡 Why This Matters

🌍 Real World

Factories help create objects in a controlled way, useful in apps that manage many similar objects like vehicles, users, or products.

💼 Career

Understanding factory patterns and companion objects is important for Kotlin developers to write clean, maintainable, and scalable code.

1

Create the Vehicle class

Create a Kotlin class called Vehicle with two properties: name of type String and type of type String. Use a primary constructor to set these properties.

Kotlin

class Vehicle(val name: String, val type: String) {
    // Your code here
}

Need a hint?

Use class Vehicle(val name: String, val type: String) to define the class and its properties.

2

Add a companion object with a factory method

Inside the Vehicle class, add a companion object. Inside it, create a function called create that takes two parameters: name and type, both of type String. The function should return a new Vehicle object using these parameters.

Kotlin

class Vehicle(val name: String, val type: String) {
    companion object {
        // Your code here
    }
}

Need a hint?

Use companion object and define fun create(name: String, type: String): Vehicle inside it.

3

Use the factory method to create a Vehicle

Outside the Vehicle class, create a variable called car and assign it the result of calling Vehicle.create with "Car" as the name and "Sedan" as the type.

Kotlin

class Vehicle(val name: String, val type: String) {
    companion object {
        fun create(name: String, type: String): Vehicle {
            return Vehicle(name, type)
        }
    }
}

// Your code here

Need a hint?

Call Vehicle.create("Car", "Sedan") and assign it to car.

4

Print the vehicle details

Write a println statement to print the text: "Vehicle: [name], Type: [type]" using the car object's name and type properties. Use a Kotlin string template.

Kotlin

class Vehicle(val name: String, val type: String) {
    companion object {
        fun create(name: String, type: String): Vehicle {
            return Vehicle(name, type)
        }
    }
}

val car = Vehicle.create("Car", "Sedan")

// Your code here

Need a hint?

Use println("Vehicle: ${car.name}, Type: ${car.type}") to print the details.