json_accessor.rb

# You don't actually need this.
# I wrote this, but rails support this 
# Use store_accessor :data, :admin

module JsonAccessor
  extend ActiveSupport::Concern

  module ClassMethods
    def json_accessor(json_attribute, *fields)
      send(:store, json_attribute, accessors: fields)

      field_methods = Module.new
      fields.each do |any_key|
        key = any_key.to_s.freeze

        field_methods.send(:define_method, "#{key}_changed?") do
          send("#{key}_change").present?
        end

        field_methods.send(:define_method, "#{key}_will_change!") do
          send("#{json_attribute}_will_change!")
        end

        field_methods.send(:define_method, "#{key}_was") do
          (send(:attribute_was, json_attribute) || {})[key]
        end

        field_methods.send(:define_method, "#{key}_change") do
          json_changes = send("#{json_attribute}_change")
          return if json_changes.nil?
          attribute_changes = json_changes.map { |change| change.try(:[], key.to_s) }
          attribute_changes.compact.present? ? attribute_changes : nil
        end

        field_methods.send(:define_method, "restore_#{key}!") do
          old_json = send("#{json_attribute}_change").try(:first) || {}
          send("#{key}=", old_json[key.to_s])
        end

        include field_methods
      end
    end
  end
end