Roll Your Own DSL with Kotlin (Lightning Talk)

Domain specific languages (DSL) are everywhere. Gradle files, the Anko library or even SQL use their own DSL. They make interacting with your product easier. And thanks to Kotlin awesome features you can create your own DSL too! In this lightning talk I will show you how to get started and create your first DSL to build a UI component.

Transcript

1. Roll your own DSL with Kotlin A lightning talk by Miquel Beltran Android Developer @ Nebenan.de @Miqubel
2. What’s a DSL? @Miqubel
3. android { compileSdkVersion 26 buildToolsVersion "26.0.2" defaultConfig { … @Miqubel
4. SELECT name FROM users WHERE age >= 30 @Miqubel
5. verticalLayout { padding = dip(32) imageView(…).lparams { margin = dip(16) gravity = Gravity.CENTER } … @Miqubel
6. // Old School Java Style val ratingView = RatingView() ratingView.setStars(3) ratingView.setMaxStars(5) // Kotlin DSL Style rating { initial = 3 maximum = 5 } @Miqubel
7. // Creating our DSL fun rating(func:() -> Unit) // Using our DSL rating({}) @Miqubel
8. // Creating our DSL fun rating(func:() -> Unit) // Using our DSL rating({ }) @Miqubel
9. // Creating our DSL fun rating(func:() -> Unit) // Using our DSL rating { } @Miqubel
10. // Creating our DSL fun rating(func:() -> Unit) // Using our DSL rating { initial = 3 maximum = 5 } @Miqubel
11. // Creating our DSL fun rating(func: RatingDsl.() -> Unit) // Using our DSL rating { initial = 3 maximum = 5 } @Miqubel
12. // Creating our DSL fun rating(func: RatingDsl.() -> Unit) class RatingDsl(var initial: Int = 1, var maximum: Int = 5) // Using our DSL rating { initial = 3 maximum = 5 } @Miqubel
13. // Creating our DSL fun rating(func: RatingDsl.() -> Unit) = RatingDsl().apply { func() } class RatingDsl(var initial: Int = 1, var maximum: Int = 5) // Using our DSL rating { initial = 3 maximum = 5 } @Miqubel
14. // Creating our DSL fun rating(func: RatingDsl.() -> Unit) = RatingDsl() .apply { func() } .build() class RatingDsl(var initial: Int = 1, var maximum: Int = 5) { fun build(): RatingView { return RatingView().apply { setStars(initial) setMaxStars(maximum) } } } // Using our DSL rating { initial = 3 maximum = 5 } @Miqubel
15. Thanks! If you would be interested in a full length talk about this, let me know! @Miqubel