[Vala] Re-entrant/Nested Iterator..

[Shawn Ferris <shawn ferris gmail com>]

Hi all --

I need a little advice. I have a database (sqlite) table that defines
a parent/child relationship. I figured the easiest way to walk the
hierarchy of the data would be to use a re-entrant (nested?) iterator.
I'd iterate over the initial statement, until I hit a row that has a
link to child records where I'd instantiate a new Iterator and start
looping through those records. I have the initial Iterator built and
can successfully return all the rows from a sqlite statement. However,
I'm struggling to visualize the re-entrant/nested piece.

I figured I'd just define a nested flag and a nested Iterator, within
the Iterator. When I hit a row that indicates there is a child query,
I'd instantiate a new Iterator, flip the nested flag to true, and then
successive calls to the parent Iterator.get/next would be chained down
to the childs Iterator.get/next methods. In this particular case, I
don't need the actual row with the child indicator, returned via the
iteratation.. However, it wouldn't hurt anything if it did. (in case
it makes a difference)

Unfortunately, I can't figure out how I'm supposed to iterate over an
Iterator w/o using a foreach loop? When I started, I figured it'd look
something like this:

class Query {
  class Iterator {
    next() {
      .. step over query ..
      if (Sqlite.DONE) return false;
      if ( record.linked_child != null ) {
        child = new Query(record.linked_child);
        nested = true;
      }
      if ( nested ) {
        var ret = child.next();
        if ( ! ret ) nested = false;
      }
      return true
    }
    get() {
      if ( nested) return child.get();
      return record;
    }
  }
}

But, it wasn't immediately obvious to me that the nested "query"
object wouldn't expose the next and get methods. I gotta believe this
is possible, but I'm surely not seeing the solution. (an elegant one
anyway) OR, if someone knows a better way to do this, I'm all ears..

As always.. I appreciate any help!

Shawn