ActiveRecord attribute serializer Hashie::Mash stored as a JSON string in Postgres

create_gadgets.rb

class CreateGadgets < ActiveRecord::Migration
  def change
    create_table "gadgets" do |t|
      t.string "info"
    end
  end
end

gadget.rb

class Gadget < ActiveRecord::Base
  serialize :info, HashieMashSerializedAsJson

  # This allows the field to be set as a Hash or anything compatible with it.
  def info=(new_value)
    self[:info] = HashieMashSerializedAsJson.new new_value
  end
end

hashie_mash_serialized_as_json.rb

# An ActiveRecord field serializer, presenting as a Mashie::Hash and stored as a JSON string in postgres.
# Of course, you need to include the hashie gem: https://github.com/intridea/hashie
class HashieMashSerializedAsJson < Hashie::Mash
  def self.dump(obj)
    ActiveSupport::JSON.encode(obj.to_h)
  end

  def self.load(json)
    new(json ? ActiveSupport::JSON.decode(json) : {}) 
  end
end