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

create_gadgets.rb

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

gadget.rb

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

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

hashie_mash_stored_as_json.rb

# An ActiveRecord field serializer, presenting as a Mashie::Hash and stored as JSON in postgres.
# Note that since the column type in Postgres is JSON, the value returned by the database
# client is in fact a Hash, which we then encapsulate as a Mashie::Hash. In the other direction, we set
# the column attribute normally by encoding as JSON, which Postgres parses and stores as data.
# Of course, you need to include the hashie gem: https://github.com/intridea/hashie
class HashieMashStoredAsJson < Hashie::Mash
  def self.dump(obj)
    ActiveSupport::JSON.encode(obj.to_h)
  end

  def self.load(raw_hash)
    new(raw_hash || {}) 
  end
end