module ActiveRecord::AttributeMethods::Serialization::ClassMethods

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 SerializationTypeMismatch 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

# File activerecord/lib/active_record/attribute_methods/serialization.rb, line 52
def serialize(attr_name, class_name_or_coder = Object)
  include Behavior

  # When ::JSON is used, force it to go through the Active Support JSON encoder
  # to ensure special objects (e.g. Active Record models) are dumped correctly
  # using the #as_json hook.
  coder = if class_name_or_coder == ::JSON
            Coders::JSON
          elsif [:load, :dump].all? { |x| class_name_or_coder.respond_to?(x) }
            class_name_or_coder
          else
            Coders::YAMLColumn.new(class_name_or_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

Returns a hash of all the attributes that have been specified for serialization as keys and their class restriction as values.

# File activerecord/lib/active_record/attribute_methods/serialization.rb, line 20