From: "Ara.T.Howard" <ahoward@...>
Date: 2004-07-30T23:51:46+09:00
Subject: Re: defined? in ruby-1.9

On Fri, 30 Jul 2004, Mark Sparshatt wrote:

> 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

ah - hadn't thought of that.  that it better than failing silently.

cheers.

-a
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