Rails - Mar 2008 - Should I use iterations to display sub categories?

Hello,

I have a categories table that has an id and a category_id so that I can
have a :belongs_to on itself.

On the left of my website I would like to display the main categories,
then their sub categories below them.

I have read in the book I have that iterations may be a possibility.

I thought that perhaps there are other ways to do this such has having
in my controller have two instance variables, one would have categories
where category_id is null to display top categories, then the other
variable would would have categories where category_id = a certain id.

Of course I just thought that the above mentioned might not work because
what about if I added a top category, then I would have to hard code
something each time - not desirable.

So what are your suggestions after readin my babble?
-- 
Posted via http://www.ruby-forum.com/.

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Joel Slowik wrote:
> Hello,
> 
> I have a categories table that has an id and a category_id so that I can
> have a :belongs_to on itself.
> 
> On the left of my website I would like to display the main categories,
> then their sub categories below them.
> 
> I have read in the book I have that iterations may be a possibility.
so far, so good. that''s the best way to do it
> I thought that perhaps there are other ways to do this such has having
> in my controller have two instance variables, one would have categories
> where category_id is null to display top categories, then the other
> variable would would have categories where category_id = a certain id.
you would need more instance vars. one for each sub-category. since most 
likely you don''t know in advance how many that would be...

> Of course I just thought that the above mentioned might not work because
> what about if I added a top category, then I would have to hard code
> something each time - not desirable.
> 
> So what are your suggestions after readin my babble?
you first load all cats with category_id 0, then iterate over children 
and so on. if necessary, in a recursive function but it''s more likely, 
that you''ll know the deepness of nested cats, than their amount.
still easier, than making guesses about the number of categories and 
needed variables
-- 
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You might want to look at acts_as_tree (now a plugin) -- it does what
you''re asking.

With your current design you might consider this:

class Category < ARec:Base
 
has_many :subcategories, :class_name=>''Category'',
:foreign_key=>''category_id''
  ...
end

You''ll gain some db efficiency since you can do your initial fetch as:

  @categories Category.find(:all, :conditions=>{:category_id=>nil},
:include=>:subcategories)

That will fetch all the ''main'' categories and their immediate
subcategories.

On Mar 7, 8:26 am, Joel Slowik
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
> Hello,
>
> I have a categories table that has an id and a category_id so that I can
> have a :belongs_to on itself.
>
> On the left of my website I would like to display the main categories,
> then their sub categories below them.
>
> I have read in the book I have that iterations may be a possibility.
>
> I thought that perhaps there are other ways to do this such has having
> in my controller have two instance variables, one would have categories
> where category_id is null to display top categories, then the other
> variable would would have categories where category_id = a certain id.
>
> Of course I just thought that the above mentioned might not work because
> what about if I added a top category, then I would have to hard code
> something each time - not desirable.
>
> So what are your suggestions after readin my babble?
> --
> Posted viahttp://www.ruby-forum.com/.
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