serialize_typed_attributes

This is a Ruby gem for Rails, to add typed getter and setter fields for the keys in an ActiveRecord object's serialized Hash.

Let's say you have an object similar to below, which uses an hstore column called properties as a hash. (ActiveRecord::Coders::Hstore comes from the activerecord-postgres-hstore gem.)

class Car
  serialize :properties, ActiveRecord::Coders::Hstore
end

The problem is an hstore field can only store string keys and values, so everything is cast to a string when the hash is persisted.

car = Car.new
car.properties = { "colour" : "red", "wheels": 4, "engine_cc": 1.8 }
car.properties["colour"]
# "red"
car.properties["wheels"]
# "4"

With this gem, you can add the following to your class description:

class Car
  serialize :properties, ActiveRecord::Coders::Hstore

  serialize_typed_attribute :properties, :colour, :string
  serialize_typed_attribute :properties, :wheels, :integer
  serialize_typed_attribute :properties, :engine_cc, :float
  serialize_typed_attribute :properties, :miles_travelled, :decimal
  serialize_typed_attribute :properties, :ownership_history, :json
end

And now you can access the properties of the hash directly as attributed accessors, cast to the field specified.

car = Car.new
car.properties = { "colour" : "red", "wheels": 4, "engine_cc": 1.8 }
car.colour
# "red"
car.wheels
# 4

Importantly, for us anyway, it provides rudimentary dirty tracking, so you can check car.colour_changed? after setting it.

Running the tests

Set test/database.yml to a Postgres database with hstore extension present (CREATE EXTENSION hstore;). Run rake test.