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ActiveRecord extension which adds typecasting to store accessors
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Store Attribute

ActiveRecord extension which adds typecasting to store accessors.

Compatible with Rails 4.2 and Rails 5+.

Extracted from not merged PR to Rails: rails/rails#18942.


In your Gemfile:

# for Rails 5+ (6 is supported)
gem "store_attribute", "~> 0.5.0"

# for Rails 4.2
gem "store_attribute", "~> 0.4.0"


You can use store_attribute method to add additional accessors with a type to an existing store on a model.

store_attribute(store_name, name, type, options)


  • store_name The name of the store.
  • name The name of the accessor to the store.
  • type A symbol such as :string or :integer, or a type object to be used for the accessor.
  • options (optional) A hash of cast type options such as precision, limit, scale, default.

Type casting occurs every time you write data through accessor or update store itself and when object is loaded from database.

Note that if you update store explicitly then value isn't type casted.


class MegaUser < User
  store_attribute :settings, :ratio, :integer, limit: 1
  store_attribute :settings, :login_at, :datetime
  store_attribute :settings, :active, :boolean
  store_attribute :settings, :color, :string, default: "red"
  store_attribute :settings, :data, :datetime, default: -> { }

u = false, login_at: "2015-01-01 00:01", ratio: "63.4608")

u.login_at.is_a?(DateTime) # => true
u.login_at =, 1, 1, 11, 0, 0)
u.ratio # => 63 # => false
# Default value is set
u.color # => red
# A dynamic default can also be provided # => Current time
# And we also have a predicate method # => false

# After loading record from db store contains casted data
u.settings["login_at"] ==, 1, 1, 11, 0, 0) # => true

# If you update store explicitly then the value returned
# by accessor isn't type casted
u.settings["ratio"] = "3.141592653"
u.ratio # => "3.141592653"

# On the other hand, writing through accessor set correct data within store
u.ratio = "3.141592653"
u.ratio # => 3
u.settings["ratio"] # => 3

You can also specify type using usual store_accessor method:

class SuperUser < User
  store_accessor :settings, :privileges, login_at: :datetime

Or through store:

class User < ActiveRecord::Base
  store :settings, accessors: [:color, :homepage, login_at: :datetime], coder: JSON
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