get class module

class source

require 'rails'

module OtherModule
  def self.included(base)
    base.extend(ClassMethods)
  end
  
  module ClassMethods
    def module
      ("::"+self.to_s.split("::").tap {|m| m.pop }.join('::')).constantize
    end
    
    def foo
      puts "I know your module #{self.module}"
    end
  end
end

module ModuleName
  module SubModule
    class MyClass
      include OtherModule
    end
  end
end

example of use

1.9.3-p0 :079 > ModuleName::SubModule::MyClass.foo
I know your module ModuleName::SubModule
 => nil