loicdescotte

##MixedTweets

We will see how to mix 2 twitter searches and push the results to the browser in real time.

First, checkout this mini project

To try it, you need to install Play 2.0

###Controller

loicdescotte

#Play2 : Les Iteratees expliqués aux humains... francophones!

Disclaimer : Ce qui suit est la traduction d'un article anglophone paru sur le blog mandubian.com

Vous pouvez retrouver l'article original ici

Vous avez probablement remarqué une nouvelle fonctionnalité intrigante de Play2 nommée Iteratee (ainsi que ses compagnons Enumerators et Enumeratee). Le but de cet article est d'essayer de rendre le concept d'Iteratee compréhensible pour le plus grand nombre avec des arguments simples, en évitant l'approche mathématique / fonctionnelle.

Cet article ne prétend pas tout expliquer à propos des Iteratee / Enumerator / Enumeratee mais traite plutôt les idées qui se cachent derrière.

loicdescotte

Scala for comprehension translation helper

"For comprehension" is a another syntaxe to use map, flatMap and withFilter (or filter) methods.

yield keyword is used to aggregate values in the resulting structure.

This composition can be used on any type implementing this methods, like List, Option, Future...

loicdescotte

import java.util.Arrays;

public class Lambda {
    public static void main (String[] args){
        Arrays.asList("aaa", "bbb", "ccc", "abb").stream()
        .filter((String w) -> w.startsWith("a"))
        .forEach(w -> System.out.println(w));
    }
}

loicdescotte

Higher order function to write stuffs in a file, with automatic resources management

Code

  def printToFile(f: java.io.File)(op: java.io.PrintWriter => Unit) {
    val p = new java.io.PrintWriter(f)
    try { op(p) } finally { p.close() }
  }

loicdescotte

Higher order function to write stuffs in a file, with automatic resources management

Code

  def printToFile(f: java.io.File)(op: java.io.PrintWriter => Unit) {
    val p = new java.io.PrintWriter(f)
    try { op(p) } finally { p.close() }
  }

loicdescotte

Scala pattern matching example

Value matching

def f(x: Int): String = x match {
  case 1 | 2 => "one or two"
  case 3 => "three"
  case _ => "other values"
}

loicdescotte

Chunck by chunk

def  transform = Action {
    
     val fileStream: Enumerator[Array[Byte]] = {
         Enumerator.fromFile(new File("data.txt"))
     }
     
     val transfo = Enumeratee.map[Array[Byte]]{byteArray =>  

loicdescotte

//val xmlNode = xml.XML.loadFile("xxx")

val xmlNode =
<persons>
	<person age="30">
		<name>bob</name>
	</person>
	<person age="40">
		<name>joe</name>
	</person>

loicdescotte

val f: Future[Int] = Future {
  if(math.random < 0.5) 1 else throw new Exception("Oh no")
} recover {
  case ex:Exception => {
    println(ex.getMessage)
    -1
  }
}

f map println