Introduction to Type-Safe Builders: create a DSL in Kotlin

In this talk we discover what DSLs are and how we can manage to build them in Kotlin. Building a DSL in Kotlin is just about manipulating known Kotlin features such as lambdas, extension functions, infix functions ect.

Transcript

1. D A K A R A N D R O I D U S E R G R O U P Introduction to Type-Safe Builders: Create a DSL in Kotlin
2. Android, Kotlin, Java, Python and other stuff Hello! I Am Rygel Louv GitHub: @rygelouv Twitter: @rygellouv Medium: @rygel
3. Domain SpecificLanguage ?
4. “DSLs are small languages, focused on a particular aspect of a software system. You can't build a whole program with a DSL, but you often use multiple DSLs in a system mainly written in a general purpose language” “ Martin Fowler
5. External Internal Particular form of API in a host general purpose language Parsed independently of the host general purpose language Two types of DSL
6. CSS DSL we already know Gradle scripts SQL External External Internal
7. Build a DSL in Kotlin Extension Functions Use of lambdas outside of parenthesis Lambdas with Receivers Scope Control with @DslMarker Infix functions
8. What does a DSL in kotlin look like ? 1
9. Anko
10. Ktor
11. Gradle Kotlin DSL
12. Kotlin Coroutines Builders
13. When or where should I create a DSL ? “A good place to use DSLs could be a configuration class or a library interface where the user doesn’t have to be aware of the models.” Fré Dumazy
14. 1 ---> Set as your DLS should look like 2 ---> Create function with lambda as parameter 3 ---> Use that function with lambda outside of parentheses 4 ---> Get rid of the "it" by changing the lambda block into a lambda with receiver 4' ---> We can one-line the expression using apply 5 ---> In order to use val and have proper data class, setup Builder Pattern for those data class 6 ---> Move Object creation functions in model class Builder 7 ---> List of Object ? Create a collection object in the builder change the function to be an "add" of item to the collection 8 ---> Want to change the collection style ? Create helper class. Subclass of list (of the object we want to create) 9 ---> Protect the DSL safety by scoping it with @DslMarker based annotation Raw steps to build our DSL
15. Stop talking Just show me The Code
16. https://github.com/rygelouv/dsl-experiment
17. You can find me at: GitHub: @rygelouv Twitter: @rygellouv Medium: @rygel Any questions? Thanks!