Play Enumerator, Iterator cheatsheet

gistfile1.scala

// --- cheat sheet ---
// 
// Enumerator &> -> filters the output of the enumerator through an Enumeratee
// Enumerator >>> -> alias for andThen; adds the output of the second enumerator after the first one is done
// Enumerator |>> -> feeds the output of the enumerator into the given iteratee for processing
// --- end of cheat sheet ---

// Example

// Iteratee that sums up the size of the input:
val inputLength = Iteratee.fold[Array[Byte], Int](0) { (length, bytes) => length + bytes.size }

// enumerator that generates strings
val stringEnumerator = Enumerator("one", "two", "three", "four")

// enumeratee that converts output from an enumerator of type String into Array[Byte]
val toByteArray = Enumeratee.map[String] { s => s.getBytes }

// let's hook them up
val countInput = stringEnumerator &> toByteArray |>> inputLenght

// ---

// enumerator that generates some random data every X seconds
val dataGenerator = Enumerator.fromCallback { () =>
   Promise.timeout(Some(new java.util.Random().nextInt(100)), 5000 milliseconds)
}

// enumeratee that converts ints to strings
val toStr = Enumeratee.map[Int] { x => x.toString }

// iteratee that prints input to the console
val toConsole = Iteratee.foreach[String](println(_))

// and now we wire all together
dataGenerator &> toStr |>> toConsole