Question

I want to write a generic helper method:

def using(closeable: [B has close() method], callback: [B has close() method] => A): A {
  try {
    callback(closeable)
  } finally {
    closeable.close()
  }
}

with the intent being that I can use this with anything that has a close() method:

using(new FileInputStream(...)) {
  stream => stream.read()
}

using(dataSource.getConnection) {
  conn => using(conn.createStatement()) {
    statement => using(statement.executeQuery("...")) {
      rs => rs.getString(1)
    }
  }
}

What I’m looking for is how this is named, such that I could have searched for the syntax myself, and the syntax itself.

Answer 1

Debilski is right, the syntax for that would be closable: { def close() }

Edit: Here’s a link to an alternative Scala implementation of the .NET like using construct you want to use based on an object and it’s apply method.