From: Xeno Campanoli on
Thank you Josh and Thomas. The source of this question is my study of Erlang,
where all 'Variables' do not vary after the initial assignment. I realized when
reading up on the language that there are many areas in my classes where the
thing I use, especially with Object Variables, are effectively constants, so I
would do best to have them as actual constants. It turns out there is a lot of
value in knowing that something cannot change, even if it can change but will
have at least an obvious error. I don't expect to Erlangize my programs, but I
have already identified things I can do to make my stuff safer and clearer just
by making class and object variables into constants. Too bad there is not a
special prefix for these as there is for the variables. That would be nice for
referencing things. Still, no big deal.


Josh Cheek wrote:
> On Wed, Apr 14, 2010 at 8:40 PM, Thomas Volkmar Worm <tvw(a)> wrote:
>> Am Wed, 14 Apr 2010 20:00:54 -0500 schrieb Xeno Campanoli:
>>> I am reading up in other areas, and it occurs to me much of the items I
>>> have as class and object variables really should be constants, but
>>> ideally still in the class or object context. Is there a way to do
>>> this?
>>> xc
>> In class context you could do:
>> class MyClass
>> def initialize
>> end
>> end
>> But I wonder, whether it makes sense at all to have constants at object
>> level. This sounds weird to me.
>> Thomas
> I do for things that don't (or shouldn't) change. For example, I'm working
> on a Rails project where the admin can assign a level of trust to a user
> such that they can post images directly to the main page from Twitter. The
> database doesn't inherently support enumerated types, so the attribute is an
> integer, then I have class level constants that map those values to their
> meanings, and a set of methods that allow you to get booleans back when
> asking if that user is able to do that authorized thing, and they are
> embedded into named scopes so that I can pull all users who have this
> authorization level, or that authorization level, and so forth. So I just
> store a single integer in the database, but my application interprets it the
> same across every instance.

"It's the preponderance, stupid!" - Professor Stephen Schneider, IPCC member