From: Arlen Christian Mart Cuss <celtic@...>
Date: 2007-10-27T23:50:14+09:00
Subject: Re: Truth value evaluating of an object

Hi,

On Sat, 2007-10-27 at 23:35 +0900, Dave River wrote:
> I know that there is a method called __bool__ in Python. You can define
> your __bool__ method in your class. The truth value of an object is
> based on the return value of __bool__. Does ruby provide similar
> mechanism?

I don't think I'm speaking out of school when I say that there's no such
way to do so.

Ruby and libraries likely rely on 'if obj' returning false if it's false
or nil - overriding this behaviour will probably cause some strange
behaviour which may result in your object being inadvertently modified!

Instead, just make an accessor like ok?, so you can test "if x.ok?".

If you need some way to test this across several objects, consider this:

class Object
  def ok?
    self
  end
end
class AreYouOk
  def ok?
    @ok
  end
end

Thus 'if x.ok?' returns the same as 'if x' for any object, but @ok for
yours!

Cheers
Arlen