From: Robert Klemme <shortcutter@...>
Date: 2010-08-19T21:42:56+09:00
Subject: Re: Check existence of object and it's property at the same time

2010/8/19 Jesús Gabriel y Galán <jgabrielygalan@gmail.com>:
> On Wed, Aug 18, 2010 at 11:47 PM, Cory Patterson <coryp@aquasun.com> wrote:
>> David,
>>
>> You are completely correct.  I guess that was a bad example.  So the
>> order of the conditions is important:
>>>> if @member and @member.is_active?; end
>> => nil
>>>> if @member.is_active? && @member; end
>> NoMethodError: undefined method `is_active?' for nil:NilClass
>>
>
> Yes, it's important. Ruby starts evaluating from left to right, and
> will shortcircuit on the first value that would make the whole
> expression false (or true if it's an "or").

For the record: short circuiting also happens in Enumerable#any? and
#all?.  And btw, the same short circuiting is done in Java and I guess
most modern languages.

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/