Convert flatfile.io output (key-value map) to CSV string.

flatfile_io_json2csv.rb

require 'csv'
require 'json'

def flatfile_io_json2csv_string(data_as_string = '[{"sku_code": "123"}, {"sku_code": "321"}]')
  CSV.generate do |csv|
    json_data = JSON.parse(data_as_string)

    csv << json_data.first.keys # header
    json_data.each do |hash|
      csv << hash.values
    end
  end
end