From: Robert Klemme <shortcutter@...>
Date: 2006-05-13T00:10:46+09:00
Subject: Re: An inherent mismatch when creating dynamic classes

2006/5/12, Eli Bendersky <eliben@gmail.com>:
> Class names in Ruby must begin with a capital litter, like constants:
>
> class poke
> end
>
> ==> ERROR: class/module name must be CONSTANT
>
> On the other hand, dynamic assignment to constants is illegal:
>
> def foo
>         Joe = 5
>         p Joe
> end
>
> ==> ERROR: dynamic constant assignment
>
> So suppose I have some method 'make_class' that returns a dynamically
> created class. I can do (outside a method):
>
> def make_class
>         Class.new
> end
>
> Bobik = make_class()
>
> argh = Bobik.new
> p argh.class
>
> ==> Bobik
>
> Nice... But inside a method / class:
>
> def make_class
>         Class.new
> end
>
> def try_it
>         Bobik = make_class()
> end
>
> ==> ERROR: dynamic constant assignment
>
> However, I can do:
>
> def make_class
>         Class.new
> end

This method is superfluous.  You can simply do "bobik = Class.new" in
this method:

> def try_it
>         bobik = make_class()
>         argh = bobik.new
>         p argh.class
> end
>
> try_it
>
> ==> #<Class:0x2c17010>
>
> This looks like a mismatch between two unrelated features (true,
> assigning to constants dynamically is fishy, but creating new classes
> isn't !), right ?

I don't see the problem.  How can unrelated features mismatch?  Also:
Constant assignments are simply not allowed in method bodies.

> And why the class name 'Bobik' is printed, while #<Class:0x2c17010> is
> printed when the class name is in lowercase. Does the lowercase change
> anything semantically ?

Uppercase names are constants and this involves some magic.  Consider:

>> c = Class.new
=> #<Class:0x829f4b0>
>> c.name
=> ""
>> Foo = c
=> Foo
>> c.name
=> "Foo"

Classes do not have a proper name until assigned a constance.  But
otherwise they are fully functional.  No problem with that.

Cheers

robert

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