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module ActiveRecord
module AttributeMethods
module Serialization
extend ActiveSupport::Concern
included do
# Returns a hash of all the attributes that have been specified for
# serialization as keys and their class restriction as values.
class_attribute :serialized_attributes, instance_accessor: false
self.serialized_attributes = {}
end
module ClassMethods
##
# :method: serialized_attributes
#
# Returns a hash of all the attributes that have been specified for
# serialization as keys and their class restriction as values.
# If you have an attribute that needs to be saved to the database as an
# object, and retrieved as the same object, then specify the name of that
# attribute using this method and it will be handled automatically. The
# serialization is done through YAML. If +class_name+ is specified, the
# serialized object must be of that class on retrieval or
# <tt>SerializationTypeMismatch</tt> will be raised.
#
# A notable side effect of serialized attributes is that the model will
# be updated on every save, even if it is not dirty.
#
# ==== Parameters
#
# * +attr_name+ - The field name that should be serialized.
# * +class_name_or_coder+ - Optional, a coder object, which responds to `.load` / `.dump`
# or a class name that the object type should be equal to.
#
# ==== Example
#
# # Serialize a preferences attribute.
# class User < ActiveRecord::Base
# serialize :preferences
# end
#
# # Serialize preferences using JSON as coder.
# class User < ActiveRecord::Base
# serialize :preferences, JSON
# end
#
# # Serialize preferences as Hash using YAML coder.
# class User < ActiveRecord::Base
# serialize :preferences, Hash
# end
def serialize(attr_name, class_name_or_coder = Object)
coder = if [:load, :dump].all? { |x| class_name_or_coder.respond_to?(x) }
class_name_or_coder
else
Coders::YAMLColumn.new(class_name_or_coder)
end
decorate_attribute_type(attr_name, :serialize) do |type|
Type::Serialized.new(type, coder)
end
# merge new serialized attribute and create new hash to ensure that each class in inheritance hierarchy
# has its own hash of own serialized attributes
self.serialized_attributes = serialized_attributes.merge(attr_name.to_s => coder)
end
end
end
end
end
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