export_to_csv.rb

require 'active_support'
require 'csv'

module ExportToCsv
  extend ActiveSupport::Concern

  def to_csv(attributes = attribute_names)
    raise 'must have attributes like %w[id created_at]' unless attributes.is_a? Array

    # 엑셀에서 csv 파일을 열었을 때 utf8을 사용하도록 BOM 표식 추가
    head = 'EF BB BF'.split(' ').map{ |a| a.hex.chr }.join()

    CSV.generate(csv = head) do |csv|
      csv << attributes
      all.each do |row|
        if block_given?
          yield row
        else
          csv << attributes.map{ |attr| row.send(attr) }
        end
      end
    end
  end
end

ActiveRecord::Base.send :extend, ExportToCsv