From: daz <dooby@...10.karoo.co.uk>
Date: 2004-02-16T15:59:56+09:00
Subject: Re: accessing constants from class methods


> David A. Black wrote:
>
> >OK, it's probably something simple but I'm staring and staring at the
> >original code, and its output (which is the same as daz's code), and I
> >can't figure out why it wasn't OK.
> >
> >Explanations welcome :-)
> >
>

Your post didn't get through to the NG, David.
Ara probably didn't see it and there appeared to be no replies
when I posted.

http://groups.google.com/groups?hl=en&th=5677a0c1234ad853


I'm wary about the defined? keyword -- I can't find a good
definition of what service it provides.


for i in 0..1   # (avoiding new scope)
  puts defined? a
                a = 1
  puts defined? a
  puts '-' * 10
end

#-> nil
#-> local-variable
#-> ----------
#-> nil
#-> local-variable
#-> ----------

## Strangely, for constants it works differently.

for i in 0..1
  puts defined? X
                X = 1
  puts defined? X
  puts '-' * 10
end

#-> nil
#-> constant
#-> ----------
#-> constant
#-> constant
#-> ----------

## The next test made me wonder if I can believe anything, any more.

for i in 0..1
  puts defined? Z
    const_set   Z, 1
  puts defined? Z
  puts '-' * 10
end

#-> nil
#-> C:/TEMP/rb3273.TMP:17: uninitialized constant Z (NameError)
#->   from C:/TEMP/rb3273.TMP:15:in `each'
#->   from C:/TEMP/rb3273.TMP:15

=begin
--------------------------------------------------------------- Module#const_set
     mod.const_set( aSymbol, anObject ) -> anObject
--------------------------------------------------------------------------------
     Sets the named constant to the given object, returning that object.
     Creates a new constant if no constant with the given name previously existed.
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     [...]
=end


daz