Define attribute which value is loaded and stored lazily. Ie. You want to get some data from a 3rd party API call but instead of setting them explicitly you want to get those on demand. Here are few lines of code to get it workable.

lazy_attribute.rb

module Concerns
  module LazyAttribute
    extend ActiveSupport::Concern

    included do
      class_attribute :lazy_attributes
    end

    module ClassMethods
      def attr_lazy(name, &logic_impl)
        sym                       = name.to_sym
        self.lazy_attributes      ||= {}
        self.lazy_attributes[sym] = logic_impl

        create_lazy_getter(sym)
      end

      def create_lazy_getter(name)
        class_eval <<-CODE, __FILE__, __LINE__
          def #{name}
            val = self.read_attribute(:#{name})
            return val if val.present?

            logic = self.lazy_attributes[:#{name}]
            val = self.instance_eval &logic

            self.update_column :#{name}, val if val
            val
          end
        CODE
      end
    end
  end
end

some_model.rb

class SomeModel < ActiveRecord::Base
  include Concerns::LazyAttribute
  
  attr_lazy :some_data do
    # Do some expensive API call or calculation or whatever make sense to you.
  end
  
end