void ServiceBuilding::deliverService()
{
  // make a service walker and send him to his wandering
  ServiceWalkerPtr serviceman = ServiceWalker::create( _getCity(), getService() );
  serviceman->setMaxDistance( getWalkerDistance() );
  serviceman->send2City( BuildingPtr( this ) );

  if( !serviceman->isDeleted() )
  {
    addWalker( serviceman.as<Walker>() );
  }
}