Scala iteratee to write to a file

Question

I have a method save that takes an Iteratee it and saves some data to it. Inside the method, the data is available as an enumerator producing byte-array chunks.

def save[E](consumer: Iteratee[Array[Byte], E]): Future[E] = {
  val producer: Enumerator[Array[Byte]] = // ...
  Iteratee.flatten(producer(consumer)).run
}

Wanted: Call save in order to have it write the data to a FileOutputStream.

I tried the following but am not sure whether this is the way to go:

def writeToStream(s: OutputStream) =
  Iteratee.foreach((e: Array[Byte]) => s.write(e)).
    mapDone(r => { s.close(); r })
save(writeToStream(new FileOutputStream(myFile)))

Question: Is this the way it's supposed to be done? I fear that this will not always close the stream (case of exceptions).

I am using the Play Framework Iteratee library from Play Framework 2.1 (which uses Scala futures).

Markus Markus · Accepted Answer · 2014-01-11T23:30:22

The scaladocs for Iteratee say that it is in the responsibility of the "producer" not the iteratee to handle resources:

The Iteratee does not do any resource management (such as closing streams); the producer pushing stuff into the Iteratee has that responsibility.

You might be successful using the "onDoneEnumerating" method in Enumerator to clean up resources afterwards.

Scaladoc Iteratee

Scala iteratee to write to a file

1 Answers