after.rb

def cities_in_region(region_id)  
  Regions.lookup(region_id)
    .or(Left("Couldn't find region #{region_id}"))
    >-> region { region.bounding_box }
    .or(Left("Region #{region_id} has no bounding box"))
    >-> bounding_box { GeoNames.search_cities(bounding_box) }
end

before.rb

def cities_in_region(region_id)  
  begin
    region = Regions.lookup(region_id)
  rescue GeoNames::ApiError => e
    raise "Error looking up region #{region_id}: #{e.message}"
  end

  if region
    if bounding_box = region.bounding_box
      begin
        response = GeoNames.search_cities(bounding_box)
        response.fetch(“cities”, []).map { |hash|
          City.new(hash)
        }
      rescue GeoNames::ApiError => e
        raise "Error searching cities in #{bounding_box}: #{e.message}"
      end
    else
      raise "Region #{region_id} doesn't have a bounding box"
    end
  else
    raise "Couldn't find region #{region_id}"
  end
end