gistfile1.txt

class Foo < ActiveRecord::Base
end

class Class
  def inherits_from?(klass)
    raise ArgumentError.new("argument must be of type Class") unless klass.is_a? Class
    if klass == self
      true
    elsif self.superclass.is_a? Class
      self.superclass.inherits_from? klass
    else
      false
    end
  end
end

Foo.inherits_from? ActiveRecord::Base