Seven Languages in Seven Weeks: A Pragmatic Guide to Learning Programming Languages (Ruby 3rd)

f.rb

#!/usr/bin/env ruby
# -*- coding: utf-8 -*-

module ActsAsCsv

  class CsvRow
    def initialize(headers, arr)
      @headers = headers
      @arr = arr
    end

    def method_missing(name, *args)
      @arr[@headers.index(name.to_s)] # name.class == Symbol なので、.to_s が必要
    end
  end

  def self.included(base)
    base.extend ClassMethods
  end

  module ClassMethods
    def acts_as_csv
      include InstanceMethods
    end
  end

  module InstanceMethods

    def read
      @csv_contents = []
      filename = self.class.to_s.downcase + '.txt'
      file = File.new(filename)
      @headers = file.gets.chomp.split(', ')

      file.each do |row|
        @csv_contents << CsvRow.new(@headers, row.chomp.split(', '))
      end
    end

    def each
      @csv_contents.each do |csv_row|
        yield(csv_row)
      end
    end

    attr_accessor :headers, :csv_contents

    def initialize
      read
    end
  end
end

class RubyCsv  # no inheritance! You can mix it in
  include ActsAsCsv
  acts_as_csv
end

m = RubyCsv.new
# puts m.headers.inspect
# puts m.csv_contents.inspect

m.each {|row| puts row.one}

f.rb-result.txt

bash$ cat rubycsv.txt 
one, two
lions, tigers
bash$ ./f.rb
lions
bash$