finalize

If a class defines a finalize method, when an instance of that class is garbage-collected that method will be invoked:

class Foo
  def finalize
    # Invoked when Foo is garbage-collected
    puts "Bye bye from #{self}!"
  end
end

# Prints "Bye bye ...!" for ever
loop do
  Foo.new
end

Note: the finalize method will only be invoked once the object has been fully initialized via the initialize method. If an exception is raised inside the initialize method, finalize won't be invoked. If your class defines a finalizer, be sure to catch any exceptions that might be raised in the initialize methods and free resources.