Hashify helper for ActiveRecord models

json_hashifier.rb

module JsonHashifier

  # Converts an ActiveRecord model object to a JSON appropriate Hash.
  # @param [Hash] options
  # @option options [String] :timezone The timezone to apply to the created_at & updated_at columns
  # @option options [Integer] :timezone_offset The timezone offset that should be used to determine the timezone
  # @option options [String] :date_format The strftime format to apply to the created_at & updated_at columns
  # @option options [Boolean] :indifferent_access Indicates whether or not to return a HashWithIndifferentAccess
  # @options options [Array<String,Symbol>] :whitelist A white list of attributes to keep in the Hash. Defaults to all attributes.
  # @options options [Array<String,Symbol>] :methods A list of methods to invoke for inclusion in the Hash.
  #   Note that the method must not accept any arguments.
  def hashify_for_json(options={})
    options[:timezone_offset] = options[:timezone_offset].to_i
    if options[:timezone].blank?
      timezone_names = ActiveSupport::TimeZone::MAPPING.keys.select do |name|
        ActiveSupport::TimeZone[name].utc_offset == options[:timezone_offset]
      end
      options[:timezone] = timezone_names.first || "UTC"
    end

    options[:date_format] ||= "%a, %b %d, %Y %I:%M %p"
    attrs = attributes
    attrs = HashWithIndifferentAccess.new(attrs) if options[:indifferent_access]

    attrs = attrs.merge(
      :created_at => (created_at.in_time_zone(options[:timezone]).strftime(options[:date_format]) rescue nil),
      :updated_at => (updated_at.in_time_zone(options[:timezone]).strftime(options[:date_format]) rescue nil)
    )

    if options[:whitelist]
      method = options[:whitelist].first.is_a?(String) ? :to_s : :to_sym
      attrs.keep_if { |k, v| options[:whitelist].nil? || options[:whitelist].include?(k.send(method)) }
    end

    (options[:methods] || []).each {|m| attrs[method] = send(m) }

    attrs
  end

end

# Example useage

# app/models/user.rb
class User < ActiveRecord::Base
  include JsonHashifier
end

# app/controllers/users_controller.rb
class UsersController < ApplicationController
  def index
    @users = User.all.map do |user|
      user.hashify_for_json(:indifferent_access => true)
        .merge(:some_number_for_example => rand(10))
    end
  end
end