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require 'active_support/core_ext/hash/indifferent_access'
module ActiveRecord
# 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.
#
# 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 PostgreSQL specific columns like +hstore+ or +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.
#
# Examples:
#
# class User < ActiveRecord::Base
# store :settings, accessors: [ :color, :homepage ], coder: JSON
# end
#
# u = User.new(color: 'black', homepage: '37signals.com')
# u.color # Accessor stored attribute
# 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'
#
# # Add additional accessors to an existing store through store_accessor
# class SuperUser < User
# store_accessor :settings, :privileges, :servants
# end
#
# The stored attribute names can be retrieved using +stored_attributes+.
#
# User.stored_attributes[:settings] # [:color, :homepage]
#
# == 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 <tt>super</tt>
# 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
module Store
extend ActiveSupport::Concern
included do
class_attribute :stored_attributes, instance_accessor: false
self.stored_attributes = {}
end
module ClassMethods
def store(store_attribute, options = {})
serialize store_attribute, IndifferentCoder.new(options[:coder])
store_accessor(store_attribute, options[:accessors]) if options.has_key? :accessors
end
def store_accessor(store_attribute, *keys)
keys = keys.flatten
_store_accessors_module.module_eval do
keys.each do |key|
define_method("#{key}=") do |value|
write_store_attribute(store_attribute, key, value)
end
define_method(key) do
read_store_attribute(store_attribute, key)
end
end
end
# assign new store attribute and create new hash to ensure that each class in the hierarchy
# has its own hash of stored attributes.
self.stored_attributes = {} if self.stored_attributes.blank?
self.stored_attributes[store_attribute] ||= []
self.stored_attributes[store_attribute] |= keys
end
def _store_accessors_module
@_store_accessors_module ||= begin
mod = Module.new
include mod
mod
end
end
end
protected
def read_store_attribute(store_attribute, key)
accessor = store_accessor_for(store_attribute)
accessor.read(self, store_attribute, key)
end
def write_store_attribute(store_attribute, key, value)
accessor = store_accessor_for(store_attribute)
accessor.write(self, store_attribute, key, value)
end
private
def store_accessor_for(store_attribute)
@column_types[store_attribute.to_s].accessor
end
class HashAccessor
def self.read(object, attribute, key)
prepare(object, attribute)
object.public_send(attribute)[key]
end
def self.write(object, attribute, key, value)
prepare(object, attribute)
if value != read(object, attribute, key)
object.public_send :"#{attribute}_will_change!"
object.public_send(attribute)[key] = value
end
end
def self.prepare(object, attribute)
object.public_send :"#{attribute}=", {} unless object.send(attribute)
end
end
class StringKeyedHashAccessor < HashAccessor
def self.read(object, attribute, key)
super object, attribute, key.to_s
end
def self.write(object, attribute, key, value)
super object, attribute, key.to_s, value
end
end
class IndifferentHashAccessor < ActiveRecord::Store::HashAccessor
def self.prepare(object, store_attribute)
attribute = object.send(store_attribute)
unless attribute.is_a?(ActiveSupport::HashWithIndifferentAccess)
attribute = IndifferentCoder.as_indifferent_hash(attribute)
object.send :"#{store_attribute}=", attribute
end
attribute
end
end
class IndifferentCoder # :nodoc:
def initialize(coder_or_class_name)
@coder =
if coder_or_class_name.respond_to?(:load) && coder_or_class_name.respond_to?(:dump)
coder_or_class_name
else
ActiveRecord::Coders::YAMLColumn.new(coder_or_class_name || Object)
end
end
def dump(obj)
@coder.dump self.class.as_indifferent_hash(obj)
end
def load(yaml)
self.class.as_indifferent_hash(@coder.load(yaml || ''))
end
def self.as_indifferent_hash(obj)
case obj
when ActiveSupport::HashWithIndifferentAccess
obj
when Hash
obj.with_indifferent_access
else
ActiveSupport::HashWithIndifferentAccess.new
end
end
end
end
end
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