Question

I’m developing a “script generator” to automatize some processes at work.
It has a Rails application running on a server that stores all data needed to make the script and generates the script itself at the end of the process.

The problem I am having is how to export the data from the ActiveRecord format to Plain Old Ruby Objects (POROs) so I can deal with them in my script with no database support and a pure-ruby implementation.

I thought about YAML, CSV or something like this to export the data but it would be a painful process to update these structures if the process changes. Is there a simpler way?

Ty!

Answer 1

By “update these structures if the process changes”, do you mean changing the code that reads and writes the CSV or YAML data when the fields in the database change?

The following code writes and reads any AR object to/from CSV (requires the FasterCSV gem):

def load_from_csv(csv_filename, poro_class)

  headers_read = []
  first_record = true
  num_headers = 0
  transaction do 
    FCSV.foreach(csv_filename) do |row|
      if first_record
        headers_read = row 
        num_headers = headers_read.length
        first_record = false
      else
        hash_values = {}

        for col_index in 0...num_headers
          hash_values[headers_read[col_index]] = row[col_index]
        end
        new_poro_obj = poro_class.new(hash_values) # assumes that your PORO has a constructor that accepts a hash. If not, you can do something like new_poro_obj.send(headers_read[col_index], row[col_index]) in the loop above
        #work with your new_poro_obj 
      end
    end
  end

end

#objects is a list of ActiveRecord objects of the same class
def dump_to_csv(csv_filename, objects)

  FCSV.open(csv_filename,'w')  do |csv|
    #get column names and write them as headers
    col_names = objects[0].class.column_names()
    csv << col_names
    objects.each do |obj|
      col_values = []
      col_names.each do |col_name|
        col_values.push obj[col_name]
      end
      csv << col_values
    end
  end

end