From: Florian Gilcher <flo@...>
Date: 2008-05-23T15:33:13+09:00
Subject: Re: Prevent ruby constant variables from changing?

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On May 22, 2008, at 6:51 PM, Mark Wilden wrote:

> On May 22, 2008, at 4:38 AM, Florian Gilcher wrote:
>>
>> If you noticed, class names are constants. As you can change  
>> classes at runtime, constants must be changable.
>> Actually overwriting Constants emits a warning. A you should  
>> program warnings-free, that should be no problem :).
>
> Sure, you can change classes at runtime, but should you be able to  
> change which object is referenced by a class name? I haven't heard  
> of that before. Do you have a real-world example of someone doing  
> that? Just curious.
>
> ///ark
>

"Hot code replace" comes to my mind. Completely reloading a class  
while keeping the system running. There, it makes sense to completely  
obliterate the old class.

Actually, this is how the RoR class-reloading in development mode  
works. They clear all loaded application classes so that they are  
loaded again by the classloader upon need. (via const_missing)


About "class name". Yes, #name is just a method. So is #instance_eval  
and #type and almost every other method. So you could argue that there  
is no such thing as evaluation in an instance context or a type as  
language features. On that standpoint, you could argue that there are  
no classes in ruby, because Ruby only exists of undefinable masses:

===
class Object
   def class
     "undefinable mass"
   end
end
===

Lets put it like that: In most sane Ruby systems, #name is either the  
name of the constant a class was bound to or "", the first being named  
(with a "class name"), the other one anonymous (or call it "ad-hoc",  
if you prefer). Also, the inability of #name to tell you the internal  
name of a class doesn't mean that it doesn't have one. This may be a  
verbal convention and not be enforcemed by the interpreter, but it is  
a common and reasonable concept. I see no use in oh-so-cool nitpicking  
that makes it much harder for not-so-zen rubyists to follow discussions.

Regards,
Florian Gilcher
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