class Object

def acts_like?(duck)

we want to act like Time simply need to define an acts_like_time? method.
x.acts_like?(:date) to do duck-type-safe comparisons, since classes that
acts_like_time?. As a result, we can do x.acts_like?(:time) and
to define an acts_like_date? method, and extends Time to define
A duck-type assistant method. For example, Active Support extends Date 
def acts_like?(duck)
  case duck
  when :time
    respond_to? :acts_like_time?
  when :date
    respond_to? :acts_like_date?
  when :string
    respond_to? :acts_like_string?
  else
    respond_to? :"acts_like_#{duck}?"
  end
end