Rails - Jun 2005 - Newbie questions (acts_as_tree && scaffolds; multi-key uniqueness)

Hello,

I''m a newbie to rails  (and still somewhat of a newbie to ruby itself);
still I hope that my questions doesn''t immediately qualify as TO
stupid...

I''m trying to build a simple app (sort of my own personally glorified 
event calendar). I would like to assign each event to a region that it 
takes place in (e.g. central London, sw London, west London, ...), and
I''d
like to order the places in a hierarchy.

I''ve created a simple model "area"

 	CREATE TABLE areas (
 	  id            INT             NOT NULL auto_increment,
 	  parent_id     INT             NULL,
 	  name          varchar(40)     NOT NULL,
 	  description   varchar(40)     NULL,

 	  PRIMARY KEY  (id),
 	  CONSTRAINT fk_area FOREIGN KEY (parent_id) REFERENCES areas(id),
 	  CONSTRAINT fk_subarea UNIQUE INDEX ( parent_id, name )
 	)

The basic initial entries I generated make up the following areas:

 	UK
 	 \- London
 		\- central
 			\- Earl''s Court
 			\- South Kensington
 		\- sw
 			\- Richmond
 			\- Twickenham
 		\- w
 			\- Chiswick
 			\- Ealing


I then generated a scaffold (./script/generate scaffold Area Admin) for 
the area model and updated the Area model to be

 	class Area < ActiveRecord::Base
 	  acts_as_tree :order => name
 	  validates_presence_of :name
 	end

After starting the server (./script/server), looking at the list of 
regions, I can''t see how the regions are linked; also, when I want to 
create a new region, I can''t specify the parent_id.


Is there any (simple/existing) way to get the scaffold generator to 
generate a scaffold that will address this?  Or do acts_as_tree / 
acts_as_list need to be handled manually?


Also, as can be seen in the DDL for the area table, there is a unique 
index on parent + name  (i.e. I would foresee that town names may be 
duplicate (or that you might want to add
''n'',''e'',''s'',''w'',''central''
regions to several cities (without having to specify distinct names for 
each city) - but each parent should only have one of these areas as an 
immediate child.

If I see it correctly, ''validates_uniqueness_of :parent_id,
:name'' will
require EACH listed attribute individually to be unique. Is there a good 
way to specify that a set of attributes needs to be unique?



   Benedikt

--
                     Gaudeo te illud de me rogavisse.

> After starting the server (./script/server), looking at the list of  
> regions, I can''t see how the regions are linked; also, when I want
> to create a new region, I can''t specify the parent_id.
>
> Is there any (simple/existing) way to get the scaffold generator to  
> generate a scaffold that will address this?  Or do acts_as_tree /  
> acts_as_list need to be handled manually?
>
Yes, they need to be handled manually.  The same goes for any  
associations that you make, such as has_many.  Scaffolding does not  
assume to know what you mean in those cases.
> Also, as can be seen in the DDL for the area table, there is a  
> unique index on parent + name  (i.e. I would foresee that town  
> names may be duplicate (or that you might want to add  
>
''n'',''e'',''s'',''w'',''central''
regions to several cities (without having
> to specify distinct names for each city) - but each parent should  
> only have one of these areas as an immediate child.
>
> If I see it correctly, ''validates_uniqueness_of :parent_id,
:name''
> will require EACH listed attribute individually to be unique. Is  
> there a good way to specify that a set of attributes needs to be  
> unique?
 From a message by Dee Zsombar, dated May 5th:
> validates_uniqueness_of :title, :scope => :author_id,    :message
> => "A book already exists with this title and author"
Duane Johnson
(canadaduane)




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