Module: ActiveRecord::Store
Overview
Store gives you a thin wrapper around serialize for the purpose of storing hashes in a single column. It’s like a simple key/value store baked into your record when you don’t care about being able to query that store outside the context of a single record.
You can then declare accessors to this store that are then accessible just like any other attribute of the model. This is very helpful for easily exposing store keys to a form or elsewhere that’s already built around just accessing attributes on the model.
Every accessor comes with dirty tracking methods (key_changed?
, key_was
and key_change
) and methods to access the changes made during the last save (saved_change_to_key?
, saved_change_to_key
and key_before_last_save
).
NOTE: There is no key_will_change!
method for accessors, use store_will_change!
instead.
Make sure that you declare the database column used for the serialized store as a text, so there’s plenty of room.
You can set custom coder to encode/decode your serialized attributes to/from different formats. JSON, YAML, Marshal are supported out of the box. Generally it can be any wrapper that provides load
and dump
.
NOTE: If you are using structured database data types (e.g. PostgreSQL hstore
/json
, or MySQL 5.7+ json
) there is no need for the serialization provided by .store. Simply use .store_accessor instead to generate the accessor methods. Be aware that these columns use a string keyed hash and do not allow access using a symbol.
NOTE: The default validations with the exception of uniqueness
will work. For example, if you want to check for uniqueness
with hstore
you will need to use a custom validation to handle it.
Examples:
class User < ActiveRecord::Base
store :settings, accessors: [ :color, :homepage ], coder: JSON
store :parent, accessors: [ :name ], coder: JSON, prefix: true
store :spouse, accessors: [ :name ], coder: JSON, prefix: :partner
store :settings, accessors: [ :two_factor_auth ], suffix: true
store :settings, accessors: [ :login_retry ], suffix: :config
end
u = User.new(color: 'black', homepage: '37signals.com', parent_name: 'Mary', partner_name: 'Lily')
u.color # Accessor stored attribute
u.parent_name # Accessor stored attribute with prefix
u.partner_name # Accessor stored attribute with custom prefix
u.two_factor_auth_settings # Accessor stored attribute with suffix
u.login_retry_config # Accessor stored attribute with custom suffix
u.settings[:country] = 'Denmark' # Any attribute, even if not specified with an accessor
# There is no difference between strings and symbols for accessing custom attributes
u.settings[:country] # => 'Denmark'
u.settings['country'] # => 'Denmark'
# Dirty tracking
u.color = 'green'
u.color_changed? # => true
u.color_was # => 'black'
u.color_change # => ['black', 'green']
# Add additional accessors to an existing store through store_accessor
class SuperUser < User
store_accessor :settings, :privileges, :servants
store_accessor :parent, :birthday, prefix: true
store_accessor :settings, :secret_question, suffix: :config
end
The stored attribute names can be retrieved using .stored_attributes.
User.stored_attributes[:settings] # [:color, :homepage, :two_factor_auth, :login_retry]
Overwriting default accessors
All stored values are automatically available through accessors on the Active Record object, but sometimes you want to specialize this behavior. This can be done by overwriting the default accessors (using the same name as the attribute) and calling super
to actually change things.
class Song < ActiveRecord::Base
# Uses a stored integer to hold the volume adjustment of the song
store :settings, accessors: [:volume_adjustment]
def volume_adjustment=(decibels)
super(decibels.to_i)
end
def volume_adjustment
super.to_i
end
end
Defined Under Namespace
Modules: ClassMethods Classes: HashAccessor, IndifferentCoder, IndifferentHashAccessor, StringKeyedHashAccessor