Quick demonstration on how to create temporary anonymous classes as well as how to extend them

anonymous_class.rb

# encoding: UTF-8
# frozen_string_literal: true

Metric = Class.new do
  def destroy
    puts 'Metric destroyed'
  end
end

MetricWithFiber = Class.new(Metric) do
  def destroy
    super
    puts 'MetricWithFiber destroyed'
  end
end

instance = MetricWithFiber.new
instance.destroy

Running this:

ruby ./anonymous_class.rb

produces:

Metric destroyed
MetricWithFiber destroyed