Rails - Dec 2004 - Re: Rails Digest, Vol 3, Issue 7

Jeremy,

Thanks. Just as I received your post I found that I was having a major 
brain freeze and forgetting to assign a "name" value to the submit 
buttons.

This is what happens when you rely on "components" and
"frameworks" to
handle the low level functionality which is actually very simple.

One of the reasons I am so excited by Rails is that a lot of the 
platforms for web development seem to be inverted mountains. They have 
tons or code sitting between you and fairly simple techniques.

--
Lon

Hi,

Is there a feature to freeze variable assignment?

e.g.
a="hello"
a.assignfreeze
a="goodbye"  # ===> generates exception

Or, in a related vein, a type freeze, so that only similar objects can be added.

I realize that constants offer assignment freezing to a certain degree. 

The reason I ask, is that I stepped over-top of some framework
variables today, and it was hard to find out what was going on. Where
as ruby protects keywords, it would be nice if frameworks or custom
domain specific languages could do the same.

Thanks,
Nick

* Nicholas Van Weerdenburg (vanweerd-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org)
[041205 21:54]:
> Is there a feature to freeze variable assignment?
> 
> e.g.
> a="hello"
> a.assignfreeze
> a="goodbye"  # ===> generates exception
> 
> Or, in a related vein, a type freeze, so that only similar objects can be
added.
> 
> I realize that constants offer assignment freezing to a certain degree. 
Nick, 
Would this be different from Ruby''s #freeze method?

Rick
-- 
 http://www.rickbradley.com    MUPRN: 911
                       |  do something quite
   random email haiku  |  similar, and much saner.
                       |  I''m quite sure that Mr.

On 05 Dec 2004, at 18:51, Nicholas Van Weerdenburg wrote:
> Hi,
>
> Is there a feature to freeze variable assignment?
>
> e.g.
> a="hello"
> a.assignfreeze
> a="goodbye"  # ===> generates exception
No.  All variables in Ruby are references.  You could do this via a 
proxy object, but that probably wouldn''t work well in this case.
> Or, in a related vein, a type freeze, so that only similar objects can 
> be added.
You could do this with a subclass of the container, but then you lose 
the beauty of Duck Typing brought to you by Ruby''s dynamic typing.
> I realize that constants offer assignment freezing to a certain degree.
Any object can be frozen, which prevents modification to it, but not to 
its contained objects:

$ ruby
a = [''foo'']
a.freeze
a[0] << '' bar''
a << ''baz''
-:4:in `<<'': can''t modify frozen array (TypeError)
         from -:4
> The reason I ask, is that I stepped over-top of some framework
> variables today, and it was hard to find out what was going on.
The best answer is to be more careful, because nobody likes to shoot 
themselves in the foot.
> Where as ruby protects keywords, it would be nice if frameworks or 
> custom
> domain specific languages could do the same.
My (personal) best advice is to get cozy with unit testing.  You can 
flush out these kinds of problems more reliably than learning a domain 
specific language and the framework you''re using.  The DSL will still 
give you ample opportunity for foot-shooting.

Plus you get automatic protection from foot-shooting as your test 
library grows. You''ve already covered all the places you shot yourself 
in the past, preventing their reoccurrence.