gakuzzzz

scala> import scala.collection._
import scala.collection._

scala> import scala.collection.JavaConverters._
import scala.collection.JavaConverters._

scala> val m: mutable.ConcurrentMap[Int, Int] = new java.util.concurrent.ConcurrentHashMap().asScala
m: scala.collection.mutable.ConcurrentMap[Int,Int] = Map()

scala> val m2 = m.withDefault(2*)

gakuzzzz

case class Area(code: String, name: String)
object Area {
  val Japan: Set[Area] = Set(
    Area("01", "北海道"),
    Area("02", "青森県")
    // ...
  )

  val Us: Set[Area] = Set(
    Area("AK", "Alaska")

gakuzzzz

name := "scala-io-test"

version := "0.1"

scalaVersion := "2.9.2"

resolvers ++= Seq(
  "typesafe-repo" at "http://repo.typesafe.com/typesafe/releases/",
  "scala-tools" at "https://oss.sonatype.org/content/groups/scala-tools/"
)

gakuzzzz

Twitter-Util Futureでのトランザクションを考える

やりたいこと

def findUser(screenName: String): Future[User] = ... 
def findFollowers(user: User): Future[Set[User]] = ...
def unfollowAtRandom(user: User, followers: Set[User]): Future[Unit] = ...

gakuzzzz

sealed trait FoldResult[+A]
case class Continue[+A](a: A) extends FoldResult[A]
case class End[+A](a: A) extends FoldResult[A]

class LimitFoldable[+A](underlying: Traversable[A]) {
  def limitFoldLeft[B](init: B)(f: (B, A) => FoldResult[B]): B = {
    @tailrec
    def fold(sentinel: B, rest: Traversable[A]): B = {
      if (rest.isEmpty) return sentinel
      f(sentinel, rest.head) match {

gakuzzzz

• 1秒後, 5秒後, 15秒後, 60秒後 みたいなリトライがしたかったので interval に Stream[Int] を渡せるようにしてみた。
• 無限 Stream 渡したら無限 retry もできるね。

gakuzzzz

public interface EntityContext {

  Object get();
  void set(Object entity);
  void remove();

}

gakuzzzz

case class User(id: String, name: String, options: Seq[String]) {
  def options(os: String*): User = copy(options = options ++ os)
}
case class Group(id: String, name: String, subgroups: Seq[Group], options: Seq[String]) {
  def options(os: String*): Group = copy(options = options ++ os)
}

gakuzzzz

// これはNG

public class User {

  private String name;
  private int age;

  public User(String name, int age) {
    this.name = name;
    this.age = age;

gakuzzzz

scala> val hoge: (Int, Int, Int) => Int = {
     |   case (0, _, 1) => 2
     |   case (_, _, _) => 3
     | }
hoge: (Int, Int, Int) => Int = <function3>

scala> hoge(0, 2, 1)
res0: Int = 2