Serializable Attribute

serializable.rb

module Serializable
  extend ActiveSupport::Concern

  module ClassMethods
    def dump(obj)
      return if obj.nil?

      assert_valid_value obj
      ActiveSupport::JSON.encode obj
    end

    def load(json)
      return if json.nil?
      attrs = ActiveSupport::JSON.decode(json) rescue json

      return attrs if attrs.is_a?(self)
      self.new.tap do |obj|
        obj.attributes = attrs
      end
    end

    private
    def assert_valid_value(obj)
      unless obj.nil? || obj.is_a?(self)
        raise ActiveRecord::SerializationTypeMismatch,
              "Attribute was supposed to be a #{self}, but was a #{obj.class}. -- #{obj.inspect}"
      end
    end
  end

  def attributes=(params)
    unless params.nil? || params.is_a?(Hash)
      raise TypeError, "expected a Hash argument, but was #{params.class}"
    end

    params.each do |attr, value|
      # instance_variable_set("@#{attr}", value) create extra attribute if it's not exists,
      # whereas +public_send+ only use pre-define attributes
      self.public_send("#{attr}=", value)
    end if params
  end

  def attributes
    instance_values
  end
end

usage.rb

# Migration
class CreateFoos < ActiveRecord::Migration
  def change
    create_table :foos do |t|
      t.json :one
    end
  end
end

# Model
class Foo < ActiveRecord::Base
  serialize :attr, Address
end

# Serializable Attribute
class Address
  include Serializable

  attr_accessor :street, :city, :country
end

a = Address.new.tap do |obj|
  obj.attributes = {"street":"282 Kevin Brook","city":"Imogeneborough","country":"French Guiana"}
end
f = Foo.new attr: a
f.save