From: Joshua Ballanco <jballanc@...>
Date: 2009-12-23T14:39:13+09:00
Subject: Re: newbie: if is not null else...

On Dec 22, 2009, at 5:55 AM, Giampiero Zanchi wrote:

> ciao
> waiting for a confirmation from the forum guys...
> 
> since nil is false in Ruby
> 
> x = a_value if x.nil?
> equals
> x = a_value if x == false
> and also
> x = a_value unless x
> or
> x ||= a_value

Not exactly...

>> x = nil
=> nil
>> x.nil?
=> true
>> x == false
=> false
>> puts "Hi!" unless x
Hi!
=> nil
>> x = false
=> false
>> x.nil?
=> false
>> x == false
=> true
>> puts "Hi!" unless x
Hi!
=> nil

false and nil both evaluate to false in conditionals, everything else (including 0) evaluates to true. However, "x == false" is asking if x is exactly false. For fun, try "p false.class"...

Cheers,

Josh