From: Mark Sparshatt <msparshatt@...>
Date: 2004-07-30T21:31:19+09:00
Subject: Re: defined? in ruby-1.9

Ara.T.Howard wrote:

> On Fri, 30 Jul 2004, Yukihiro Matsumoto wrote:
>
>> Hi,
>>
>> In message "defined? in ruby-1.9"
>>    on 04/07/30, "Dmitry V. Sabanin" <sdmitry@lrn.ru> writes:
>>
>> |Lately I was converting some of my projects to ruby 1.9, and I found 
>> that this code is no longer working:
>> |  raise if defined?(Test::Unit)
>> |Throws:
>> |  uninitialized constant Test (NameError)
>> |
>> |Ruby 1.8 silently works with that code. So, how do I need to handle 
>> this kind of checks in 1.9?
>> |For now as a workaround I changed Test::Unit to Test and it works  
>> fine.
>>
>> Because 1.8 silently ignores NameError in the check for Test::Unit.
>>
>>                             matz.
>
>
> but isn't that what 'defined?' is for?  to determine if the compiler 
> has seen
> a 'name' yet?
>
I supposed the rational is that by running

defined?(Test::Unit)

You are checking if the Test class/module contains a constant Unit. If 
Test doesn't exist then Ruby can't check this, so it throws a NameError.

The obvious, though verbose, workaround would be to do

defined?(Test) && defined(Test::Unit)

--
Mark Sparshatt