Rails - May 2005 - Noob: can I get a list of unique attributes with ActiveRecord?

Railers,

 

I have a simple blog app with a model for ‘Article’ that has a ‘created’
column in sqlite (datetime).

 

I’d like to build a helper that gives me a collection of “month” objects
representing the months for which articles exist, each with a 3 attributes:
a text ‘description’ of “month-year”, and the ‘month’ and ‘year’ numbers I
need to construct the appropriate url for each.

 

I can do strftime, my prob is figuring out how to pull back the list of
months. I don’t really want to have to do Article.find :all then try and
parse out the months with Ruby (not exactly efficient on the db). Is there
an easy way to do this in ActiveRecord?

 

Thanks in advance for the the tips.


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On 17.5.2005, at 01:55, Ben Stovold wrote:
> Railers,
>  
> I have a simple blog app with a model for ‘Article’ that has a  
> ‘created’ column in sqlite (datetime).
>  
> I’d like to build a helper that gives me a collection of “month”  
> objects representing the months for which articles exist, each with a  
> 3 attributes: a text ‘description’ of “month-year”, and the ‘month’  
> and ‘year’ numbers I need to construct the appropriate url for each.
>  
> I can do strftime, my prob is figuring out how to pull back the list  
> of months. I don’t really want to have to do Article.find :all then  
> try and parse out the months with Ruby (not exactly efficient on the  
> db). Is there an easy way to do this in ActiveRecord?
I don''t think so. I would create a class method that uses select_all  
[1] (i.e. pure sql) to return the months:

select distinct month(created_at) as month,
		year(created_at) as year,
		concat(monthname(created_at), '' '', year(created_at) ) as
description
from news;

Make sure you have an index for these (if that''s possible in your db),
otherwise the query can become pretty expensive when the size of the  
table grows.

[1]  
http://rails.rubyonrails.com/classes/ActiveRecord/ConnectionAdapters/ 
AbstractAdapter.html#M000543

//jarkko

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



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Thanks Jarkko.

Gotta say, seems like quite a bit of work for what strikes me as a
potentially common requirement, ie. reading/manipulating values for an
attribute across a model. I''m surprised there''s not an easier
way to
do this in Active Record.

Gives me pause: am I approaching the problem the wrong way?

I simply want to be able to construct unordered list of the months my
articles were published, with a link to the appropriate archive
page...

Cheers again,
Ben.

On 5/17/05, Jarkko Laine <jarkko-k1O+Gnc6WpmsTnJN9+BGXg@public.gmane.org>
wrote:
> On 17.5.2005, at 01:55, Ben Stovold wrote:
> 
> > Railers,
> > 
> > I have a simple blog app with a model for ''Article''
that has a
> > ''created'' column in sqlite (datetime).
> > 
> > I''d like to build a helper that gives me a collection of
"month"
> > objects representing the months for which articles exist, each with a
> > 3 attributes: a text ''description'' of
"month-year", and the ''month''
> > and ''year'' numbers I need to construct the
appropriate url for each.
> > 
> > I can do strftime, my prob is figuring out how to pull back the list
> > of months. I don''t really want to have to do Article.find
:all then
> > try and parse out the months with Ruby (not exactly efficient on the
> > db). Is there an easy way to do this in ActiveRecord?
> 
> I don''t think so. I would create a class method that uses
select_all
> [1] (i.e. pure sql) to return the months:
> 
> select distinct month(created_at) as month,
>                 year(created_at) as year,
>                 concat(monthname(created_at), '' '',
year(created_at) ) as description
> from news;
> 
> Make sure you have an index for these (if that''s possible in your
db),
> otherwise the query can become pretty expensive when the size of the
> table grows.
> 
> [1]
> http://rails.rubyonrails.com/classes/ActiveRecord/ConnectionAdapters/
> AbstractAdapter.html#M000543
> 
> //jarkko
> 
> --
> Jarkko Laine
> http://jlaine.net
> http://odesign.fi
> 
> 
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> 
> 
> 
>