Ruby: storing a value at inclusion time

Question

In a Ruby class, I'd like to store the value of a variable at the time it includes a given module. Below is a contrived example:

module M
  def self.included(base)
    base.class_eval do
      @@inclusion_time = Time.now

      def included_at
        @@inclusion_time
      end
    end
  end
end

class A
  include M
end

sleep 3

class B
  include M
end

sleep 3

class C
  include M
end

a = A.new
b = B.new
c = C.new

puts a.included_at
puts b.included_at
puts c.included_at

I've tried this any number of ways (attr_accessor, set_constant, etc,) but the end result is always the same. All of the classes have whatever value was set last.

How do I work around this?

Answer 1

module M
  def self.included _
    @inclusion_time = Time.now
  end
  def included_at
    self.class.instance_eval{@inclusion_time}
  end
end