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Scala-ARM for class members?

I'm very new to Scala, so please excuse my basic question.

I'm trying to get Scala-Arm to manage the release of a class member, but having trouble with scoping.

Although the following code compiles, it fails with

java.lang.NoSuchMethodError: resource.ManagedResource.reflect()Ljava/lang/Object; 

on the reflect call. So it seems the the managed_file is being released immediately.

For local variables I have used the for (managed_file <- managed(...)) syntax but I can't see what to do here.

Suggestions anyone?

class Writer(outputPath: String){

  val managed_file = managed(new FileOutputStream(new File(outputPath)))

  def write(something : SomeClass) {
    var bos = new ByteArrayOutputStream
    var dos = new DataOutputStream(bos)

    try {
      dos.write(Marshal.dump(something))
      bos.writeTo(managed_file.reflect)
    } 
    finally {
      dos.close
      bos.close
    }
  }
}

scala-arm. Return type

I'm using scala-arm library to automatically release/close resources (for example InputStream).

But the problem is that code below returns ExtractableManagedResource[Int], not just Int as I want.

val result = for(responseStream <- managed(response.getResponseBodyAsStream)) yield {
    val localResult: Int = 1
    localResult
}
// result is of type ExtractableManagedResource[Int]

Is there any option to return Int and overcome wrapping result to ExtractableManagedResource?

EDIT: I know that I can just declre result variable as var and assign to it from inside the for-comprehension, but I want more scala-idiomatic way, i.e. without using var

ScalaARM error - value filter is not a member of ManagedResource

Following the example on the ScalaARM homepage I wrote this:

for ( ir: IndexReader <- managed(DirectoryReader.open(FSDirectory.open(file)))) { ... }

(Open a lucene IndexReader)

however I get this compilation error:

Error:(34, 45) Play 2 Compiler: Indexer.scala:34: value filter is not a member of resource.ManagedResource[org.apache.lucene.index.DirectoryReader] for ( ir: IndexReader <- managed(DirectoryReader.open(FSDirectory.open(file)))) {

Can someone explain what is happening here? ^