active_model_serializers/lib/active_model_serializers/model.rb

# ActiveModelSerializers::Model is a convenient
# serializable class to inherit from when making
# serializable non-activerecord objects.
module ActiveModelSerializers
  class Model
    include ActiveModel::Model
    include ActiveModel::Serializers::JSON

    attr_reader :attributes

    def initialize(attributes = {})
      @attributes = attributes
      super
    end

    # Defaults to the downcased model name.
    def id
      attributes.fetch(:id) { self.class.name.downcase }
    end

    # Defaults to the downcased model name and updated_at
    def cache_key
      attributes.fetch(:cache_key) { "#{self.class.name.downcase}/#{id}-#{updated_at.strftime("%Y%m%d%H%M%S%9N")}" }
    end

    # Defaults to the time the serializer file was modified.
    def updated_at
      attributes.fetch(:updated_at) { File.mtime(__FILE__) }
    end

    def read_attribute_for_serialization(key)
      if key == :id || key == 'id'
        attributes.fetch(key) { id }
      else
        attributes[key]
      end
    end
  end
end