Configuration DSL pattern in Kotlin - Mini Project: Build & Apply

Build a Simple Configuration DSL in Kotlin

📖 Scenario: Imagine you are creating a small Kotlin program to configure a coffee machine. You want to set options like coffee type, size, and sugar level using a simple and readable configuration style called a DSL (Domain Specific Language).

🎯 Goal: Build a Kotlin configuration DSL that lets you set coffee options in a clear and easy way, then print the chosen settings.

📋 What You'll Learn

Create a data class called CoffeeConfig with properties type, size, and sugar.

Create a function called coffeeConfig that takes a lambda with receiver of CoffeeConfig.

Inside the lambda, allow setting the properties type, size, and sugar.

Print the final coffee configuration in a readable format.

💡 Why This Matters

🌍 Real World

Configuration DSLs make it easy to set up options in a readable way, like configuring build tools, UI components, or server settings.

💼 Career

Understanding how to create and use DSLs in Kotlin is useful for Android developers and backend engineers who want to write clean, expressive configuration code.

1

Create the CoffeeConfig data class

Create a Kotlin data class called CoffeeConfig with three mutable properties: type of type String initialized to "Espresso", size of type String initialized to "Medium", and sugar of type Int initialized to 1.

Kotlin

# Create the CoffeeConfig data class with default values
// Your code here

Need a hint?

Use data class CoffeeConfig(var type: String = "Espresso", var size: String = "Medium", var sugar: Int = 1) to create the class.

2

Create the coffeeConfig function

Create a function called coffeeConfig that takes a lambda with receiver of type CoffeeConfig and returns a CoffeeConfig object. Inside the function, create a new CoffeeConfig instance, apply the lambda to it, and return it.

Kotlin

data class CoffeeConfig(var type: String = "Espresso", var size: String = "Medium", var sugar: Int = 1)

// Create the coffeeConfig function with a lambda receiver
// Your code here

Need a hint?

Define fun coffeeConfig(block: CoffeeConfig.() -> Unit): CoffeeConfig and use config.block() to apply the lambda.

3

Use the DSL to set coffee options

Use the coffeeConfig function to create a CoffeeConfig object called myCoffee. Inside the lambda, set type to "Latte", size to "Large", and sugar to 2.

Kotlin

data class CoffeeConfig(var type: String = "Espresso", var size: String = "Medium", var sugar: Int = 1)

fun coffeeConfig(block: CoffeeConfig.() -> Unit): CoffeeConfig {
    val config = CoffeeConfig()
    config.block()
    return config
}

// Create myCoffee using coffeeConfig and set properties
// Your code here

Need a hint?

Call coffeeConfig { type = "Latte"; size = "Large"; sugar = 2 } and assign it to myCoffee.

4

Print the coffee configuration

Print the coffee configuration stored in myCoffee using println. Format the output exactly as: "Coffee type: Latte, Size: Large, Sugar: 2".

Kotlin

data class CoffeeConfig(var type: String = "Espresso", var size: String = "Medium", var sugar: Int = 1)

fun coffeeConfig(block: CoffeeConfig.() -> Unit): CoffeeConfig {
    val config = CoffeeConfig()
    config.block()
    return config
}

val myCoffee = coffeeConfig {
    type = "Latte"
    size = "Large"
    sugar = 2
}

// Print the coffee configuration
// Your code here

Need a hint?

Use println("Coffee type: ${myCoffee.type}, Size: ${myCoffee.size}, Sugar: ${myCoffee.sugar}") to print the configuration.