Dame tus tipos pegaso

Desde hace años que estamos en Karumi escribiendo código. En este tiempo hemos aprendido unas cuantas técnicas y métodos que donde a traves de los tipos reducimos los errores y hacemos el camino del desarrollo más sencillo.
Los tipos están de moda y vienen para quedarse. Enseñaremos ejemplos, código, usos y casuísticas que nos hemos encontrado en nuestro desarrollo en backend o Android y como usando la 'mítica armadura tipada' resolvemos problemas clásicos del desarrollo.
Con ejemplos de JavaScript, Python, Kotlin y Scala.

Transcript

1. Dame tus tipos pegaso Jorge Juan Barroso Carmona jorge@karumi.com @flipper83 Developer Android GDE
2. Sergio Gutierrez Pedro 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: Kotlin Training 17 Oct. Testing Training 20 Nov. Kotlin Training 12 Dec.
5. Adam Tornhill “Si compila, funciona.” Jorge J Barroso Theoretical Developer
6. Classic arguments to use or not use types.
7. Less tests (people does not write tests)
8. Fast iterations (recompiling scala project)
9. code verbosity (type inference)
10. Types are not about static vs dynamic languages. It’s about improving by modeling and adding semantic to your domain.
11. Semantic data types
12. var foo = new Foo((resolve, reject) => { setTimeout(() => { resolve('foo'); }, 300); }); foo.then((value) => { console.log(value); // expected output: "foo" }); QUESTION: WHAT IS IT?
13. var promise1 = new Promise((resolve, reject) => { setTimeout(() => { resolve('foo'); }, 300); }); promise1.then((value) => { console.log(value); // expected output: "foo" }); Promise
14. function getId(){ var user = getCurrentUser(); return user.id; }
15. function getId(){ var user = getCurrentUser(); if (user) { return user.id; } return null; }
16. Maybe function getId() { return getCurrentUser() .map(user =>user.id); } function getCurrentUser() { return Maybe.None(); //or return currentUser.some(); }
17. Maybe function get(key) { const value = Maybe.fromNull(store.get(key)); const valueTTLInMillis = store.get(getItemTTLKey(key)); const valueSaveDate = store.get(getItemSaveDateKey(key)); return value.bind(v => { const now = moment(); const diff = moment.duration(now.diff(valueSaveDate)); const timeDiffInSeconds = diff.milliseconds(); if (timeDiffInSeconds < valueTTLInMillis) { const recoveredInstance = recoverOptionals(v); return Some(recoveredInstance); } else { removeValue(key); return None(); } }); } #Pedro Vicente Gomez
18. Maybe function fetchPublications(page = 1) { return (dispatch, getState) => { dispatch(fetchingPage(page)); const maybeCachedFeedPage = get(feedPageCacheKey(page)); if (maybeCachedFeedPage.isSome()) { const feedPage = maybeCachedFeedPage.val; dispatch(feedPageLoaded(feedPage)); } else { getFeedPage(page).then(result => { if (result.isRight()) { const feedPage = result.right(); set(feedPageCacheKey(page), feedPage, feedPageTTLInMillis); dispatch(feedPageLoaded(feedPage)); } else { dispatch(errorFetchingPage(result.left())); } return result; }); } }; } #Pedro Vicente Gomez
19. Maybe function fetchPublications(page = 1) { return (dispatch, getState) => { dispatch(fetchingPage(page)); const maybeCachedFeedPage = get(feedPageCacheKey(page)); if (maybeCachedFeedPage.isSome()) { const feedPage = maybeCachedFeedPage.val; dispatch(feedPageLoaded(feedPage)); } else { getFeedPage(page).then(result => { if (result.isRight()) { const feedPage = result.right(); set(feedPageCacheKey(page), feedPage, feedPageTTLInMillis); dispatch(feedPageLoaded(feedPage)); } else { dispatch(errorFetchingPage(result.left())); } return result; }); } }; } #Pedro Vicente Gomez Is it the same as if(page) ???
20. Maybe function fetchPublications(page = 1) { return (dispatch, getState) => { dispatch(fetchingPage(page)); const maybeCachedFeedPage = get(feedPageCacheKey(page)); if (maybeCachedFeedPage.isSome()) { const feedPage = maybeCachedFeedPage.val; dispatch(feedPageLoaded(feedPage)); } else { getFeedPage(page).then(result => { if (result.isRight()) { const feedPage = result.right(); set(feedPageCacheKey(page), feedPage, feedPageTTLInMillis); dispatch(feedPageLoaded(feedPage)); } else { dispatch(errorFetchingPage(result.left())); } return result; }); } }; } #Pedro Vicente Gomez
21. New data type: Either aka Result function fetchPublications(page = 1) { return (dispatch, getState) => { dispatch(fetchingPage(page)); const maybeCachedFeedPage = get(feedPageCacheKey(page)); if (maybeCachedFeedPage.isSome()) { const feedPage = maybeCachedFeedPage.val; dispatch(feedPageLoaded(feedPage)); } else { getFeedPage(page).then(result => { if (result.isRight()) { const feedPage = result.right(); set(feedPageCacheKey(page), feedPage, feedPageTTLInMillis); dispatch(feedPageLoaded(feedPage)); } else { dispatch(errorFetchingPage(result.left())); } return result; }); } }; } #Pedro Vicente Gomez
22. Contracts
23. function getId(){ var user = getCurrentUser(); return ??? } WHAT ‘getCurrentUser’ returns?
24. Reveal intentions
25. Avoid introspection
26. function getId(){ let user = getCurrentUser(); return getCurrentUser() .map(user =>user.id); } function getCurrentUser(): Maybe<User> { return Maybe.fromNull(currentUser) } TypeScript
27. def getCurrentUser() -> Optional[User]: return currentUser return None #Union[X, None] Python
28. Type Alias
29. function getUsers(): Maybe<Array<User>> { return Maybe.fromNull(currentUsers); } —————————————————————————————————————————— type Users = Array<User>; function getUsers(): Maybe<Users> { return Maybe.fromNull(currentUsers); } TypeScript
30. function addSalary(salaryInEuros: number){…} —————————————————————————————————————————— function addSalary(salaryInEuros: Money){…} addSalary(Money.euros(33.3)); TypeScript
31. Sealed Classes
32. sealed class DomainError object class UserNotExist : DomainError() data class InvalidAccount(account: String) : DomainError() ——————————————————————————————————————————- fun InvalidAccount( domainError: DomainError): string = when (domainError) { is UserNotExist -> “No exist” is InvalidAccount -> “account ${domainError.account}” } Kotlin
33. Refined Types
34. sealed class DomainError object class UserNotExist : DomainError() data class InvalidAccount(account: String) : DomainError() type Zero = W.`0`.T type Ten = W.`10`.T type Amount = Int Refined Interval.Closed[Zero, Ten] object Amount extends RefinedTypeOps[Amount, Int] class Counter(var amount: Amount) { def increase(): Unit = Amount.from(amount.value + 1) .foreach(v => amount = v) } #Raul Raja Code 47Deg Scala
35. Adam Tornhill “Modelar es el vinagre de Módena de la ensalada, semántica es sabor que te llevas.” Pedro Gomez Technical chef
36. Bibliography They’re the cracks! TypeScript. Monet.js Comic Time.Pedro Vicente Gomez. karumi blog about kotlin. Sergio Gutierrez, Toni López. Better types = fewer tests. Raul Raja Who in Their Right Mind Would Use Monads in Clojure?. muhuk blog refined. fthomas. https://www.reddit.com/r/Python/comments/6d5haz/the_story_of_adding_type_hints_to_one_of_my/ Refinement Types for TypeScript. Panagiotis Vekris, Benjamin Cosman, Ranjit Hhala
37. Find me I am very social! jorge@karumi.com @flipper83 +JorgeJBarroso Questions?