11h30 - 12h20 - Auditorium

FLATMAP ZAT SHITLes monades expliquées aux geeks

27 au 29 mars 2013

FLATMAP ZAT SHITLes monades expliquées aux geeks

François SarradinDéveloppeur λ

@fsarradin

François Sarradin

● Développeur λ● http://kerflyn.wordpress.com/

● "Je suis un bagger"● http://www.brownbaglunch.fr/

@fsarradin

@bbl_fr

Entity x = getEntity1()

Entity y = getEntity2()

Entity z = x.get() + y.get()

Entity x = getEntity1()

Entity y = getEntity2()

Entity z = x.get() + y.get()

Asynchrone

null

Exception

Entity x = getEntity1()

Entity y = getEntity2()

Entity z = x.get() + y.get()

if (? == null)

try ...

finally

Thread

synchronized

...

if (? != null)

if (? !=

null)

try ... catch()

try ... catch()Thread

synchronized...

Entity x = getEntity1()

Entity y = getEntity2()

Entity z = x.get() + y.get()

* Conserve le code métier

Agenda

● Live coding / Scala 2.10○ Exception○ Asynchrone

● Code review / Java 8○ Exception

● Conclusion

Alice

InBank-land

Alice

Solde total ?

Service Web

Breizh BankLa PostaleBGP

BankService

Web

AccountRepository

getAccount(b, n)a:Account

JSON

Architecture

BankProxy BankProxy BankProxy

1: Get accounts

2: ???

3: PROFIT!

27 au 29 mars 2013

def balanceByBank: String = { val balancesByBankJson: Iterable[String] = for ((bankName, accountNumbers <- ownerAccounts) yield { val balances: List[Double] = for (accountNumber <- accountNumbers.toList) yield getAccount(bankName, accountNumber ).balance s"""{"name":"$bankNam e","b alan ce": "${b ala nce s. su m} "} " " " }

DémonstrationScala 2.10

Code source sur Githubhttps://github.com/fsarradin/bankapp.git

Try[A]val ok = Try { 1 }ok: scala.util.Try[Int] = Success(1)

val ko = Try { throw new Exception("#1") }ko: scala.util.Try[Nothing] = Failure(Exception: #1)

1 Try[A] 1 for-expressionfor { x <- ok } yield s"x = $x"res1: scala.util.Try[String] = Success(x = 1)

for { x <- ko } yield s"x = $x"res2: scala.util.Try[String] = Failure(Exception: #1)

2 Try[A] 1 for-expressionval ok1: Try[Int] = Success(1)val ok2: Try[Int] = Success(2)val ko1: Try[Int] = Failure(new Exception("#1"))val ko2: Try[Int] = Failure(new Exception("#2"))

for { x <- ok1; y <- ok2 } yield x + yres1: scala.util.Try[Int] = Success(3)

for { x <- ko1; y <- ok2 } yield x + yres2: scala.util.Try[String] = Failure(Exception: #1)

for { x <- ko1; y <- ko2 } yield x + yres3: scala.util.Try[String] = Failure(Exception: #1)

27 au 29 mars 2013

def balanceByBank: String = { val balancesByBankJson: Iterable[String] = for ((bankName, accountNumbers <- ownerAccounts) yield { val balances: List[Double] = for (accountNumber <- accountNumbers.toList) yield getAccount(bankName, accountNumber ).balance s"""{"name":"$bankNam e","b alan ce": "${b ala nce s. su m} "} " " " }

DémonstrationScala 2.10 : Try

Code source sur Githubhttps://github.com/fsarradin/bankapp.git

Future[A]val fshort: Future[Int] = Future { 1 }

fshort: Future[Int] = ... // illico

val flong: Future[Int] = Future { Thread.sleep(2000); 2 }

flong: Future[Int] = ... // illico

Future[A] & for-expressionfor { x <- fshort } yield s"x = $x"

res1: Future[String] ≈ Future("x = 1") // in fine

for { x <- fshort; y <- flong } yield x + y

res2: Future[Int] ≈ Future(3) // in fine

27 au 29 mars 2013

def balanceByBank: String = { val balancesByBankJson: Iterable[String] = for ((bankName, accountNumbers <- ownerAccounts) yield { val balances: List[Double] = for (accountNumber <- accountNumbers.toList) yield getAccount(bankName, accountNumber ).balance s"""{"name":"$bankNam e","b alan ce": "${b ala nce s. su m} "} " " " }

DémonstrationScala 2.10 : Future

Code source sur Githubhttps://github.com/fsarradin/bankapp.git

Try(exception)

Type monadique

Future(asynchrone)

Monade

Option(absence)

List(non-déterminisme)

Reader(depend. injection)

...

Contexte

Pureté fonctionnelleAspect technique

flatMap : opération monadique

for { x <- m}yield x + 1

for { x <- m1 y <- m2}yield x + y

m.map(x => x + 1)

m1.flatMap(x => m2.map(y => x + y ))

27 au 29 mars 2013

def balanceByBank: String = { val balancesByBankJson: Iterable[String] = for ((bankName, accountNumbers <- ownerAccounts) yield { val balances: List[Double] = for (accountNumber <- accountNumbers.toList) yield getAccount(bankName, accountNumber ).balance s"""{"name":"$bankNam e","b alan ce": "${b ala nce s. su m} "} " " " }

DémonstrationJava 8 et les monades

Code source sur Githubhttps://github.com/fsarradin/bankapp-java.git

Conclusion

● Code métier○ Peu de changement

● Système de type○ Aspect technique (déclaratif)○ Composition métier/technique => code○ Validation => compilateur

Question ?