Rails - Jan 2005 - multicolumn primary keys in activerecord

hi,

I''ve got the following tables in mysql notation:

CREATE TABLE `nodes` (
   `id` int(11) NOT NULL auto_increment,
   `parent_id` int(11) default ''0'',
   `group_id` int(11) default ''0'',
   PRIMARY KEY  (`id`),
);

CREATE TABLE `groups` (
   `parent_id` int(11) NOT NULL default ''0'',
   `id` int(11) NOT NULL auto_increment,
   PRIMARY KEY  (`parent_id`,`id`)
);

The tables have other attributes as well, but for this
question they are of little importance.

The nodes table is actually a representation of a tree
and the groups are there so that several nodes can be
grouped together. the reason why parent_id ends up in
the groups table is because the data is only allowed to
group children of the same node,

class Node < ActiveRecord::Base
         belongs_to :parent,
	           :class_name => ''Node'',
	           :foreign_key => ''parent_id''
         has_many :children,
	         :class_name => ''Node'',
	         :foreign_key => ''parent_id''
	belongs_to :group,
	           :foreign_key => ?what?
end

class Group < ActiveRecord::Base
         has_many :nodes # Here is also a problem...
end

I asked on irc, and got the tips that it might be possible
to do by overriding primary_key for the Group class, but
browsing around the code it seems a bit problematic to return
to values, since for instance passing two values to .find()
has completely different semantics.

Since my lack of experience with activerecord I don''t really
know where to start, and therefore I now ask what would be
the best way to acheive this, and where should I look for
advice?

!g

Hi Gustav,

On 7.1.2005, at 12:59, Gustav Munkby wrote:
>
> CREATE TABLE `groups` (
>   `parent_id` int(11) NOT NULL default ''0'',
>   `id` int(11) NOT NULL auto_increment,
>   PRIMARY KEY  (`parent_id`,`id`)
> );
Just one note: If your id is auto_increment, it will be unique anyway. 
Why do you need to have a two-column primary key? Actually the table is 
not in third normal form at the moment.

//jarkko

--
Jarkko Laine
http://jlaine.net
http://odesign.fi


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Finally found the answer...

After diggin the API, I realise that render_action actually load the
template with the action name, but does not execute the method. so
what I should have done is just call the ''list'' method one
more time:

    def add_item  
        @item = Todo.new  
        @item.attributes = @params["new_item"]  
        if @item.save  
            redirect_to(:action => "list")  
        else
            list  # <- call list method to load the @done and
@not_done variables
            render_action "list"
        end
    end

Is this the correct way? Rails is fun:)

On Fri, 7 Jan 2005 23:25:36 +0800, Boon Hoo Thee
<theebh-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> Finally found the answer...
> 
> After diggin the API, I realise that render_action actually load the
> template with the action name, but does not execute the method. so
> what I should have done is just call the ''list'' method
one more time:
> 
>     def add_item
>         @item = Todo.new
>         @item.attributes = @params["new_item"]
>         if @item.save
>             redirect_to(:action => "list")
>         else
>             list  # <- call list method to load the @done and
> @not_done variables
>             render_action "list"
>         end
>     end
> 
> Is this the correct way? Rails is fun:)
I believe the correct method would be to use a redirect so that it
lets rails handle calling the new controller method.  But your way
should work as well.