How to serialize a Plain-Old Ruby Object (PORO)

When you are first getting started with ActiveModelSerializers, it may seem only ActiveRecord::Base objects can be serializable, but pretty much any object can be serializable with ActiveModelSerializers. Here is an example of a PORO that is serializable in most situations:

# my_model.rb
class MyModel
  alias :read_attribute_for_serialization :send
  attr_accessor :id, :name, :level

  def initialize(attributes)
    @id = attributes[:id]
    @name = attributes[:name]
    @level = attributes[:level]
  end

  def self.model_name
    @_model_name ||= ActiveModel::Name.new(self)
  end
end

The ActiveModel::Serializer::Lint::Tests define and validate which methods ActiveModelSerializers expects to be implemented.

An implementation of the complete spec is included either for use or as reference: ActiveModelSerializers::Model. You can use in production code that will make your PORO a lot cleaner.

The above code now becomes:

# my_model.rb
class MyModel < ActiveModelSerializers::Model
  attributes :id, :name, :level
end

The default serializer would be MyModelSerializer.

IMPORTANT: There is a surprising behavior (bug) in the current implementation of ActiveModelSerializers::Model that prevents an accessor from modifying attributes on the instance. The fix for this bug is a breaking change, so we have made an opt-in configuration.

New applications should set:

ActiveModelSerializers::Model.derive_attributes_from_names_and_fix_accessors

Existing applications can use the fix and avoid breaking changes by making a superclass for new models. For example:

class SerializablePoro < ActiveModelSerializers::Model
  derive_attributes_from_names_and_fix_accessors
end

So that MyModel above would inherit from SerializablePoro.

derive_attributes_from_names_and_fix_accessors prepends the DeriveAttributesFromNamesAndFixAccessors module and does the following:

id will always be in the attributes. (This is until we separate out the caching requirement for POROs.)
Overwrites the attributes method to that it only returns declared attributes. attributes will now be a frozen hash with indifferent access.

For more information, see README: What does a 'serializable resource' look like?.

2.5 KiB Raw Blame History

How to serialize a Plain-Old Ruby Object (PORO)

2.5 KiB

Raw Blame History