public void setSeance(Seance seance) {
    if (seance == null) {
      throw new NullObjectInsertionException("Seance shouldn't be NULL.");
    }
    //TODO: do something with this crap
    if (this.seance != null && !this.seance.equals(seance)) {
      throw new ReassignObjectException("Ticket already assigned to another seance. Ticket could not be reassigned.");
    }
    if ( !seance.existsTicket(this)) {
      seance.addTicket(this);
    }
    this.seance = seance;
  }