Llevamos un año dandole duro a kotlin desde karumi tanto del lado de servidor como desde el lado de Android, y hemos descubierto muchas cosas interesantes a la hora de programar y como escribir mejor código y más sencillo en Kotlin. En esta charla eseñaremos los cambios que hemos introducido y como explotamos las ventajas de un lenguaje que viene muy fuerte, dando mucha caña y con un potencial enorme. Veremos código y muchos ejemplos y lo compararemos con código antiguo en Java. Si buscas la charla de introdución a Kotlin donde explicaremos como se escribe un elvis operator, esta no es. Find out more at https://madrid2018.codemotionworld.com/speakers/

1. Kotlin Pro-Tips
Jorge Juan Barroso Carmona
Developer and GDE
jorge@karumi.com
@flipper83

2. Sergio GutierrezPedro Gomez
Davide Mendolia
Fran Toro
Antonio Lopez

3. Testing for android & iOS.
Trainings
Architecture, Patterns and
principles for Android & iOS.
Mastering Git.
Advanced mobile development.
Testing for android & iOS.
Architecture, Patterns and
principles for Android & iOS.
Companies For Everybody
Next open:
Testing Training 23 Jun.
Kotlin Training 20 Feb.
Swift Training 26 Mar.
Arch Training 3 Apr.

5. Adam Tornhill
“Computer languages differ not so much
in what they make possible, but in what
they make easy.”
Larry Wall

6. https://github.com/Karumi/SuperHeroesKotlin
https://github.com/Karumi/play-framework-kotlin

7. Increase Readability

8. improve command
pattern

9. @Inject
public class Application extends Controller, ParseableJson
{
public Application(
private final CreateKarumiDeveloper createKarumiDeveloper,
private final GetDeveloper getDeveloper
){/**/}
public CompletionStage<Result>
getDeveloper(String developerId){
getDeveloper.execute(UUID.fromString(developerId));
/**/
}
}
Adam Tornhill
Command
Pattern
JAVA

10. class Application @Inject constructor(
private val createKarumiDeveloper:CreateKarumiDeveloper,
private val getDeveloper: GetDeveloper
) : Controller(), ParseableJson {
fun getDeveloper(developerId: String):
CompletionStage<Result> = async {
getDeveloper(UUID.fromString(developerId)).fold(
ifLeft = this::processError,
ifRight = this::ok
)
}
}
Adam Tornhill
is this a method?
or is an object?
KOTLIN

11. class GetDeveloper @Inject constructor(
private val developerDao: DeveloperDao
) {
operator fun invoke(developerId: UUID):
Either<DeveloperError, Developer> =
developerDao[developerId].fold(
ifFailure = { DeveloperError.StorageError.left() },
ifSuccess = { it.toEither{ DeveloperError.NotFound }}
)
}
Adam Tornhill
Override
operators
getSuperHeroes()
KOTLIN

12. improve Data access

13. class GetDeveloper @Inject constructor(
private val developerDao: DeveloperDao
) {
operator fun invoke(developerId: UUID):
Either<DeveloperError, Developer> =
developerDao[developerId].fold(
ifFailure = { DeveloperError.StorageError.left() },
ifSuccess = { it.toEither{ DeveloperError.NotFound }}
)
}
Adam Tornhill
KOTLIN
is this a List?

14. operator fun get(id: UUID): Try<Option<Developer>> = Try {
DeveloperEntity.DAO
.query()
.where()
.idEq(id)
.findOne()
?.toDomain()
.toOption()
}
Adam Tornhill
KOTLIN
[id]

15. Handling
Exceptions

16. public class DeveloperDao {
public Developer getById(UUID id) throws Exception {
DeveloperEntity developerEntity =
DeveloperEntity.DAO
.query()
.where()
.idEq(id)
.findOne()
return developerMapper(developerEntity);
}
}
Adam Tornhill
JAVA

17. public class DeveloperDao {
public Developer getById(UUID id) throws Exception {
DeveloperEntity developerEntity =
DeveloperEntity.DAO
.query()
.where()
.idEq(id)
.findOne()
return developerMapper(developerEntity);
}
}
Adam Tornhill
JAVA

18. public class GetDeveloper {
/**/
public Developer execute(UUID developerId) {
try {
Developer developer =
developerDao.getById(devloperId);
return developer;
} catch (Exception e) {
return null;
}
}
}
Adam Tornhill
JAVA

19. public class GetDeveloper {
/**/
public Developer execute(UUID developerId) {
try {
Developer developer =
developerDao.getById(devloperId);
return developer;
} catch (Exception e) {
return null;
}
}
}
Adam Tornhill
JAVA

20. class DeveloperDao {
operator fun get(id: UUID): Try<Option<Developer>> =
Try {
DeveloperEntity.DAO
.query()
.where()
.idEq(id)
.findOne()?
.toDomain()
.toOption()
}
}
Adam Tornhill
Kotlin

21. class DeveloperDao {
operator fun get(id: UUID): Try<Option<Developer>> =
Try {
DeveloperEntity.DAO
.query()
.where()
.idEq(id)
.findOne()?
.toDomain()
.toOption()
}
}
Adam Tornhill
Kotlin

22. class DeveloperDao {
operator fun get(id: UUID): Try<Option<Developer>> =
Try {
DeveloperEntity.DAO
.query()
.where()
.idEq(id)
.findOne()?
.toDomain()
.toOption()
}
}
Adam Tornhill
Kotlin

23. class DeveloperDao {
operator fun get(id: UUID): Try<Option<Developer>> =
Try {
DeveloperEntity.DAO
.query()
.where()
.idEq(id)
.findOne()?
.toDomain()
.toOption()
}
}
Adam Tornhill
Kotlin

24. class DeveloperDao {
operator fun get(id: UUID): Try<Option<Developer>> =
Try {
DeveloperEntity.DAO
.query()
.where()
.idEq(id)
.findOne()?
.toDomain()
.toOption()
}
}
Adam Tornhill
Kotlin

25. operator fun invoke(developerId: UUID):
Either<DeveloperError, Developer> =
developerDao[developerId]
.toEither{ DeveloperError.NotFound }
.mapLeft { StorageError }
Adam Tornhill
Kotlin

26. operator fun invoke(developerId: UUID):
Either<DeveloperError, Developer> =
developerDao[developerId]
.toEither{ DeveloperError.NotFound }
.mapLeft { StorageError }
Adam Tornhill
Kotlin
Try<Option<Developer>>

27. operator fun invoke(developerId: UUID):
Either<DeveloperError, Developer> =
developerDao[developerId]
.toEither{ DeveloperError.NotFound }
.mapLeft { StorageError }
Adam Tornhill
Kotlin

28. fun getDeveloper(developerId: String):
CompletionStage<Result> = async {
getDeveloper(UUID.fromString(developerId))
.fold(
ifLeft = this::processError,
ifRight = this::ok
)
}
Adam Tornhill
Kotlin

29. fun getDeveloper(developerId: String):
CompletionStage<Result> = async {
getDeveloper(UUID.fromString(developerId))
.fold(
ifLeft = this::processError,
ifRight = this::ok
)
}
Adam Tornhill
Kotlin

30. Compiler check

31. sealed classes

32. private fun processError(
developerError: DeveloperError
): Result =
when (developerError) {
DeveloperError.StorageError ->internalServerError()
DeveloperError.NotFound -> notFound()
DeveloperError.NotKarumier ->
badRequest("Onlykarumies")
}
Adam Tornhill
Kotlin

33. private fun processError(
developerError: DeveloperError
): Result =
when (developerError) {
DeveloperError.StorageError ->internalServerError()
DeveloperError.NotFound -> notFound()
DeveloperError.NotKarumier ->
badRequest("Onlykarumies")
}
Adam Tornhill
Kotlin

34. private fun processError(
developerError: DeveloperError
): Result =
when (developerError) {
DeveloperError.StorageError ->internalServerError()
DeveloperError.NotFound -> notFound()
DeveloperError.NotKarumier ->
badRequest("Onlykarumies")
}
Adam Tornhill
Kotlin
Compile
Error

35. sealed class DeveloperError {
object StorageError : DeveloperError()
object NotFound : DeveloperError()
object NotKarumier : DeveloperError()
}
Adam Tornhill
Kotlin

36. exhaustive

37. private fun onStatusChanged(status: Status) {
when (status) {
is Status.Idle -> {
loadingView.visibility = GONE
hideItems()
}
is Status.Fetching ->
loadingView.visibility = VISIBLE
is Status.Fetched -> {
loadingView.visibility = GONE
showItems()
}
}.exhaustive
}
Adam Tornhill
Kotlin

38. private fun onStatusChanged(status: Status) {
when (status) {
is Status.Idle -> {
loadingView.visibility = GONE
hideItems()
}
is Status.Fetching ->
loadingView.visibility = VISIBLE
is Status.Fetched -> {
loadingView.visibility = GONE
showItems()
}
}.exhaustive
}
Adam Tornhill
Kotlin
val Any?.exhaustive get() = Unit

39. Definición de modelos

40. data class Developer(
val id: UUID = UUID.randomUUID(),
val username: String,
val email: String?
)
Adam Tornhill
Kotlin
val developer = Developer(
val email = “jorge@karumi.com",
val username = “Jorge Carmona”
)
val developer = Developer(
val username = “Jorge Carmona”
)

41. Bibliography
They’re the cracks!
Clean Code. Uncle Bob. 2008
Kotlin For Android Developers. Antonio Leiva. 2015
GitHub AsyncAwait . metalabdesign.
Github funKTionale. MarioAriasC.
Kodein. Salomon Brys.
Karumi Blog and Katas on github.

42. Find meI am very social!
jorge@karumi.com
@flipper83
Questions?