How to pass object as an argument to its method in Ruby

Question

I'm trying to define factorial method for Fixnum class and I don't know how to pass this Fixnum as an argument to my method. Was trying to write something like that

def Fixnum.factorial(n)
    n > 1 ? n * factorial(n-1) : 1
end

though I knew it would be incorrect. So is there some kind of "this" reserved word to access this number?

Answer 1

Something like this:

class Fixnum
  def factorial
      self > 1 ? self * (self - 1).factorial : 1
  end
end

puts 6.factorial
# 720

You know, of course, that this is a silly method of calculating a factorial?