How do I create a class which instance can be evaluated as false? [duplicate]

This question already has answers here: How to inherit from NilClass or how to simulate similar function (3 answers) Closed 9 years ago.

I want to create a class Nilly to obtain a "pseudo-nil" object, but I need it to be evaluated开发者_JAVA百科 as boolean false.

e.g.:

class Nilly; end

n = Nilly.new

puts n ? 'true' : 'false'    #=>  I want false here

How can I do that?

P.S.: I tried to do class Nilly < NilClass, but I coudn't use the new method (it was stripped out in NilClass).

---

Boolean logic in Ruby ONLY allows nil and false to be falsy

Everything else is truthy.

There is no way to do this.

May I ask why you want this? What is special about your Nilly class?

I suggest you just call it a different way.

class Nilly
  def nil?
    true
  end
end

And use this in your logic

puts n.nil? ? 'false' : 'true'

---

Override the new method:

class Nilly < NilClass
  def Nilly.new
  end
end

n = Nilly.new
puts n ? 'true' : 'false'    #=>  I want false here

Unlike the previous two solutions, this does exactly what you want. n actually evaluates as nil, without the need to test with a nil? method. The to_s solution only works because you are putsing it, which implicitly calls to_s.