Shared via Pony Playground (https://playground.ponylang.io/?gist=6538dc2a66ad7bcb52542005f6df0d4f)

main.pony

class Movie is Comparable[Movie ref]
  """
  What we know about a movie in the library.
  """
  let id: U16
  let title: String
  let location: U16
  let actors: String
  let genre: U8

  new create( ident: U16, loc: U16, ttl: String, act: String, gen: U8 ) =>
    id = ident
    title = ttl
    location = loc
    actors = act
    genre = gen

  new from_db( data: Array[U8] val ) =>
    """
    Create the object from a database record in packed form.
    """
    var r: BinRecReader = BinRecReader
    r.append( data )

    id = data(U8(MovieField.idTAG()))
    title = data(U8(MovieField.ttlTAG()))
    location = data(U8(MovieField.locTAG()))
    genre = data(U8(MovieField.genTAG()))
    actors = data(U8(MovieField.actTAG()))

  fun pack(): Array[U8] =>
    """
    Pack all the fields into the format stored in the database.
    """
    var w: BinRecWriter = BinRecWriter
    w.add_pair( U8(MovieField.idTAG()), id )
    w.add_pair( U8(MovieField.genTAG()), genre )
    w.add_pair( U8(MovieField.ttlTAG()), title )
    w.add_pair( U8(MovieField.locTAG()), location )
    if actors.size() > 0 then
      w.add_pair( U8(MovieField.actTAG()), actors )
      end
    w.done()

  fun val lt( other: Movie ): Bool =>
    """
    Determine whether this movie should sort before another movie.
    """
    if genre < other.genre then
      return true
      end
    if title < other.title then
      return true
      end
    return false