Serializes model for use with https://github.com/rjackson/pivot.js

foo.rb

class Foo < ActiveRecord::Base
  include Pivotable
  # calls method on self, labeled as the method name
  pivot :name
  
  # calls method on self and labels it with a custom name
  pivot :some_awful_field_name, as: :a_better_field_name
  
  # Calls value from another object/method than self
  # Without the call to `as` this example would be named "some_related_object_bar", but with the `as`
  # it will just be labeled "bar"
  pivot :bar, from: :some_related_object, as: :bar
end

output.txt

Foo.first.to_pivotable_csv
#=> "name, a_better_field_name, bar\noutput, values here\n"

Foo.all.to_pivotable_csv
#=> "name, a_better_field_name, bar\noutput, values, here\nfor, each, of\nyour,records,,\n

pivotable.rb

# Serializes model for use with pivot.js
# https://github.com/rjackson/pivot.js
require 'csv'
module Pivotable
  extend ActiveSupport::Concern
  included do
    attr_reader :pivotable_attrs
    @pivotable_field_options ||= []
  end

  def pivot_attrs!
    self.class.pivotable_field_options.map do |f|
      if f[:from] == :self
        value = send(f[:field])
      else
        value = send(f[:from]).try(:send, f[:field])
      end
      { f[:as] => value }
    end.inject(&:merge)
  end

  def to_pivotable_csv(opts={})
    @pivotable_attrs ||= pivot_attrs!
    if pivotable_attrs
      CSV.generate do |csv|
        csv << pivotable_attrs.keys unless opts[:header] == false
        csv << pivotable_attrs.values
      end
    end
  end
  class UnknownKeyError < StandardError; end

  module ClassMethods
    def pivot_field(field, opts={})
      opts[:field] = field
      opts[:from] ||= :self
      opts[:as] ||= "#{opts[:from]}_#{opts[:field]}"
      opts.except(:from, :as, :field).each_key { |k| raise UnknownKeyError, "#{key}" }
      @pivotable_field_options ||= []
      @pivotable_field_options << opts
    end
    alias_method :pivot, :pivot_field

    def pivot_fields(*fields)
      fields.each {|f| pivot_field(f) }
    end

    def pivotable_field_options
      @pivotable_field_options
    end

    def to_pivotable_csv
      objects_csv = all.each.map do |s|
        s.to_pivotable_csv(header: false)
      end.inject(:<<)
      CSV.generate { |ccsv| ccsv << @pivotable_field_options.map { |o| o[:field] } } << objects_csv
    end
  end
end