When Clean Architecture met Kotlin: A love story (Vol. 2)

When Clean Architecture met Kotlin: A love story
Kotlin, a modern language bursts into the community when developers have been perfecting what they call Clean Architecture for years, some potions and spells with which to increase the power of testability and become independent of evil external agents and cruel frameworks.
While large groups begin to praise the bonanzas of lambdas, extension functions, null treatment and other songs of sirens, this language will have to fight to show that it is not just a nice syntax and promises of summer, but has come to take Clean Architecture to a new level.
Corutines, polymorphic types, high order functions, pattern matching and many other ideas and solutions are what Kotlin offers to us, and we will review them to see how to use them and continue having a Clean Architecture.

Transcript

1. When Clean Architecture Met Kotlin A love story (vol 2) A better lovestory than Twilight MONGUERS MOBILE PRESENTS A WRAPPER BROS. PRODUCTION IN ASSOCIATION WITH METRO GOLDWYN ARROW. COSTUME DESIGNER JAVISON FORD, EDITED BY KATHECLEAN HEPBURN, MUSIC BY RYAN KOTLIN Ryan Kotlin (La dataclass de Noah) Samuel Lambda Jackson (Jurassic Map) Mock Winslet (Typetanic) Emma Klaxon (Curry Potter) fantastiK!
2. Emma CleanStone
3. Javison Ford
4. Nicolás Patarino @npatarino
5. #loveStoryKotlin @npatarino
6. CleanStone Architecture
7. Clean Architecture
8. Clean Architecture • Independent of Frameworks and libraries • Independent of Database • Independent of UI • Domain centered • Testable
9. CleanStone Architecture
12. Ryan Kotlin
13. Lists val movies: List<Movie> = repository.getMovies() val result = movies.filter { it.year > 2000 } println(result)
14. Lists List<Movie> movies = repository.getMovies(); List<Movie> result = new ArrayList<>(); for (Movie element : movies) { if (element.getYear() > 2000) { result.add(element); } } System.out.println(movies);
15. Robert Guava Jr.
16. Lists Collection<Integer> collection = repository.getMovies(); Iterators.removeIf(collection.iterator(), new Predicate<Integer>() { @Overrid public boolean apply(Integer i) { return element.getYear() > 2000; } }); System.out.println(collection);
17. Lists List<Movie> movies = repository.getMovies(); List<Movie> result = movies.stream() .filter(movie -> movie.getYear() > 2000) .collect(Collectors.toList()); System.out.println(result) 8
18. Lists val movies: List<Movie> = repository.getMovies() val result = movies.filter { it.year > 2000 } println(result)
20. Lists val movies: List<Movie> = repository.getMovies() val result = movies.filter { it.year > 200 } .sortedBy { it.title } .takeLast(5) .reversed() .slice(0..3) println(result)
21. Smart Cast & Check Type if (item instanceof Movie) { println( (Movie) (item.title)) } if (item is Movie) { println(item.title) }
22. Type Inference Map<Integer, String> map = new HashMap<>(); map.put(1, "one"); map.put(2, "two"); val map = mapOf(1 to "one", 2 to "two")
26. Movie class public class Movie { private String id, title; private List<Person> characters; private int year; public Movie(final String id, final String title, final List<Person> characters, final int year) { this.id = id; this.title = title; this.characters = characters; this.year = year; } }
27. Movie class @Override public boolean equals(final Object o) { if (this == o) { return true; } if (o == null || getClass() != o.getClass()) { return false; } final Movie movie = (Movie) o; return year == movie.year && Objects.equals(id, movie.id) && Objects.equals(title, movie.title) && Objects.equals(characters, movie.characters); } @Override public int hashCode() { return Objects.hash(id, title, characters, year); }
28. Movie class @Override public String toString() { return "Movie{" + "id='" + id + '\'' + ", title='" + title + '\'' + ", characters=" + characters + ", year=" + year + '}'; }
30. Movie data class data class Movie(var id: String, var title: String, var characters: List<Person>, var year: Int)
32. Mutability MovieManager movieManager = new MovieManager(); Movie movie = new Movie("Jurassic Map", 1993); movie.setYear(2017); movieManager.doSomething(movie); Log.d(movie.getYear());
33. Immutability public void setYear(final String year) { this.year = year; } public Movie withYear(int year) { return new Movie(this.title, year); } MovieManager movieManager = new MovieManager(); Movie movie = new Movie("Jurassic Map", 1993); movie = movie.withYear(2017); movieManager.doSomething(movie); Log.d(movie.getYear());
34. Immutability data class Movie(var title: String, var year: Int) data class Movie(val title: String, val year: Int)
36. Copy objects val movie = Movie("Typetanic", 1997) val copy = movie.copy(title = "La dataclass de Noah")
37. Copy objects val movie = Movie("Typetanic", 1997) val copy = movie.copy(title = "La dataclass de Noah", year = 2005, awards = 36, compositor = "Emma Klaxon", director = "Samuel Lambda Jackson")
39. Layer objects problems
40. Mapping objects public class MovieMapper { public Movie map(final MovieEntity entity) { final int yearInt = Integer.parseInt(entity.getYear()); return new Movie(entity.getTitle(), yearInt); } }
41. Mapping objects public class MovieRepositoryImpl implements MovieRepository { ... @Nullable @Override public Movie getMovieById(final String id) { final MovieEntity entity = localDatasource.getMovieById(id); final MovieMapper mapper = new MovieMapper(); if (entity != null) { return mapper.map(entity); } else { final MovieEntity movieEntity = networkDatasource.getMovieById(id); if (movieEntity != null) { return mapper.map(movieEntity); } } return null; } }
42. Extension functions fun upperCaseFirstLetter(text: String): String { return text.substring(0,1).toUpperCase().plus(text.substring(1)) }
43. Extension functions fun String.upperCaseFirstLetter(): String { return this.substring(0, 1).toUpperCase().plus(this.substring(1)) } “maradona”.upperCaseFirstLetter()
44. Mapping objects fun MovieEntity.toDomain(): Movie = Movie(title, year) ... class MovieRepositoryData: MovieRepository { operator override fun get(id: String): Movie = localDatasource.getMovieById(id).recover { networkDatasource.getMovieById(id) }.toDomain() }
45. Mapping objects public class MovieRepositoryImpl implements MovieRepository { ... @Nullable @Override public Movie getMovieById(final String id) { final MovieEntity entity = localDatasource.getMovieById(id); final MovieMapper mapper = new MovieMapper(); if (entity != null) { return mapper.map(entity); } else { final MovieEntity movieEntity = networkDatasource.getMovieById(id); if (movieEntity != null) { return mapper.map(movieEntity); } } return null; } }
46. Operators fun MovieEntity.toDomain(): Movie = Movie(title, year) class MovieRepositoryData: MovieRepository { operator override fun get(id: String): Movie = localDatasource.getMovieById(id).recover { networkDatasource.getMovieById(id) }.toDomain() } }
47. Operators fun MovieEntity.toDomain(): Movie = Movie(title, year) class MovieRepositoryData: MovieRepository { operator override fun get(id: String): Movie = localDatasource.getMovieById(id).recover { networkDatasource.getMovieById(id) }.toDomain() } val movie = movieRepository["123456"]
48. Operator overloading a + b -> a.plus(b) a - b -> a.minus(b) a * b -> a.times(b) a[i] -> a.get(i) a[i] = b -> a.set(i, b) a() -> a.invoke() a(i) -> a.invoke(i) a += b -> a.plusAssign(b) a == b -> a?.equals(b) ?: (b === null) a > b -> a.compareTo(b) > 0 a >= b -> a.compareTo(b) >= 0
50. Mapping objects fun MovieEntity.toDomain(): Either<MappingError, Movie> = title?.let { year?.let { Right(Movie(title, year)) } ?: Left(MappingError) } ?: Left(MappingError)
52. Build time increases with Kotlin Javison Ford
53. Ryan Kotlin is kind of functional
54. Calcular el coste total (€) de un listado de tareas Petición devuelve List<TaskEntity> Parsear a List<Task> Calcular el tiempo de cada Task Calcular el coste del tiempo de cada Task Sumar todos los costes Functional Programming
55. Calculate tasks cost public Integer fullCost(List<TaskEntity> tasks) { Integer sum = 0; for (TaskEntity taskEntity : tasks) { Task task = toDomain(taskEntity); int timeSpent = task.getTimeSpent(); int timePriced = getTimePriced(timeSpent); sum += timePriced; } return sum; }
56. Reduce Map Sum Functional Programming
57. Calculate tasks cost Reduce ( AppyToAll ( ApplyToAll( ApplyToAll( tasksEntity, toDomain ), spentTime ), spentTimeInEuros ), Sum )
59. Calculate tasks cost Reduce ( Map ( Map ( Map ( tasksEntity, toDomain ), spentTime ), spentTimeInEuros ), Sum )
60. Calculate tasks cost Reduce ( Map ( Map ( Map ( tasksEntity, toDomain ), spentTime ), spentTimeInEuros ), Sum )
61. Calculate tasks cost Reduce ( Map ( Map ( listToDomain ( tasksEntity ), spentTime ), spentTimeInEuros ), Sum )
62. Calculate tasks cost Reduce ( Map ( Map ( listToDomain (tasksEntity), spentTime ), spentTimeInEuros ), Sum )
63. Calculate tasks cost Reduce ( Map ( Map ( listToDomain (tasksEntity), spentTime ), spentTimeInEuros ), Sum )
64. Calculate tasks cost Reduce ( Map ( listSpentTime ( listToDomain (tasksEntity) ), spentTimeInEuros ), Sum )
65. Calculate tasks cost Reduce ( Map ( listSpentTime ( listToDomain (tasksEntity) ), spentTimeInEuros ), Sum )
66. Calculate tasks cost Reduce ( listTimeInEuros ( listSpentTime ( listToDomain (tasksEntity) ) ), Sum )
67. Calculate tasks cost Reduce ( listTimeInEuros ( listSpentTime ( listToDomain (tasksEntity) ) ), Sum )
68. Calculate tasks cost sumAll ( listTimeInEuros ( listSpentTime ( listToDomain (tasksEntity) ) ) )
69. Calculate tasks cost private fun List<TaskEntity>.listToDomain(): List<Task> = map { it.toDomain() } private fun List<Task>.listSpentTime(): List<Int> = map { it.timeSpent } private fun List<Int>.listTimeInEuros(): List<Int> = map { getTimeInEuros(it) }
70. Calculate tasks cost fun fullCost(tasksEntity: List<TaskEntity>) = tasksEntity.listToDomain() .listSpentTime() .listTimeInEuros() .sumAll()
71. Calculate tasks cost public Integer fullCost(List<TaskEntity> tasks) { Integer sum = 0; for (TaskEntity taskEntity : tasks) { Task task = toDomain(taskEntity); int timeSpent = task.getTimeSpent(); int timePriced = getTimePriced(timeSpent); sum += timePriced; } return sum; }
73. Error handling - Java public interface Repository { Movie getMovie(String id) } public void run() { try { final Movie movie = repository.getMovie("1"); } catch (Exception e) { System.out.println("Ouch! Error: " + e.getLocalizedMessage()); } }
74. Error handling - Java public interface Repository { Movie getMovie(String id) throws IOException, NoSuchFieldException; } public void run() { try { final Movie movie = repository.getMovie("1"); } catch (NoSuchFieldException e) { System.out.println("Not movie found error: " + e.getLocalizedMessage()); } catch (IOException e) { System.out.println("Network error: " + e.getLocalizedMessage()); } }
75. Error handling - Java public interface Repository { Movie getMovie(String id) throws NetworkException, NotMovieException; } public void run() { try { final Movie movie = repository.getMovie("1"); } catch (NotMovieException e) { System.out.println("Not movie found error: " + e.getLocalizedMessage()); } catch (NetworkException e) { System.out.println("Network error: " + e.getLocalizedMessage()); } }
76. • Very expensive • Bad modelling • Should be exceptionals • Let system inconsistent • Unchecked exceptions Problems with exceptions
77. Enums public enum DatasourceError { MOVIE_NOT_FOUND, NETWORK_ERROR, FILESYSTEM_ERROR }
78. Enums public enum DatasourceError { MOVIE_NOT_FOUND(“Movie not found”), NETWORK_ERROR(“There is no internet connection”), FILESYSTEM_ERROR(“Unable to read the file”) private String error; Genre(final String error) { this.error = error; } private int getError() { return error; } }
79. • Restricted hierarchy • Enum with vitamins ◦ Several instances per class ◦ They carry states Sealed class
80. Sealed class sealed class DataSourceError { class NotFound(val id: String) : DataSourceError() object NetworkError : DataSourceError() class FilesystemError(val file: File) : DataSourceError() }
82. Either • Two values ◦ Left ◦ Right • Result in some languages (Swift) & libraries • Communicate error or success • Similar to Option or Try
83. Either sealed class Either<out L, out R> { companion object } data class Left<out L>(val error: L) : Either<L, Nothing>() data class Right<out R>(val value: R) : Either<Nothing, R>() fun <C> fold(left: (L) -> C, right: (R) -> C): C
84. Either sealed class RepositoryError { object NoInternet : RepositoryError() object UnAuthorized : RepositoryError() }
85. Either typealias ResultMovie = Either<RepositoryError, Movie> fun getMovie(id: String, movieRepository: MovieRepository) { val resultMovie: ResultMovie = movieRepository.getMovieById(id) resultMovie.fold({ handleError(it) }, { handleSuccess(it) }) } fun handleSuccess(movie: Movie) = println(movie)
86. Pattern matching fun handleError(error: RepositoryError) = when (error) { RepositoryError.NoInternet -> println("No internet connection") RepositoryError.UnAuthorized -> println("Token expired") }
89. Use cases public class GetMovie { private MovieRepository repository; private String id; public GetMovie(final MovieRepository repository, final String id) { this.repository = repository; this.id = id; } public Movie execute() { return repository.getMovieById(id); } }
90. Use cases fun getMovie(id: String, movieRepository: MovieRepository) = movieRepository.getMovieById(id)
91. Use cases fun getMovie(id: String, movieRepository: MovieRepository) = movieRepository.getMovieById(id) fun getMovies(personRepository: PersonRepository) = personRepository.getMovies() fun getPerson(id: String, personRepository: PersonRepository) = personRepository.getPerson(id) fun getPersons(personRepository: PersonRepository) = personRepository.getPersons()
94. Carrie SpringBoot Fisher
96. Execution useCase<Error, Result> { bg = tasks(tasksRepository) delay = 5000 ui = fold({ handleError() }, { handleSuccess(it) }) }.run(useCaseExecutor)
97. Execution override fun <Error, Result> execute(background: () -> Either<Error, Result>, ui: (Either<Error, Result>) -> Unit, delayed: Long): CancellationToken = JobCancellationToken(launch { delay(delayed) ui(background()) })
98. Execution override fun <Error, Result> execute(background: () -> Either<Error, Result>, ui: (Either<Error, Result>) -> Unit, delayed: Long): CancellationToken = JobCancellationToken(runBlocking { val job = launch { delay(delayed); ui(background()) } job.join(); job })
99. Execution useCase<Error, Result> { bg = tasks(tasksRepository) delay = 5000 ui = fold({ handleError() }, { handleSuccess(it) }) }.run(useCaseExecutor)
101. There is only one happiness in life, to love and be loved
103. Disclaimer
104. Questions? @npatarino
105. You map, I map Mock Dawson - Typetanic
106. La vida no se mide por las veces que compilas, sino por los momentos que te dejan sin refactor Hitch: Especialista en lambdas
107. Love means never have to search for a git blame Love gitStory
108. - You just tell me what you want, and I'm gonna be that for you - … You are functional - I could be that Ryan Kotlin - Crazy, Stupid, Code
109. Thanks for the adventure, now go have a new one (And refactor to Kotlin) Map