Firstly, I've asked a similar question before[*]. I didn't get any
answers back then, maybe now I have better luck
Let's say I have models like this
class Article < ActiveRecord::Base
has_many :versions
end
class Version < ActiveRecord::Base
belongs_to :article
default_scope order('updated_at')
scope :published, where(:state => 'published')
validates :state, :inclusion => { :in => ['draft', 'published'] }
validates :title, :content, :presence => true
end
It's easy to find the latest version for an article, just
article.versions.last
The same for published versions isn't much more complicated
articles.versions.published.last
Of course, I'm not only dealing with single articles
Article.all
Then, in a articles/_article.html.erb
<%= article.version.last.title %>
Oops! That triggers another database access for each article.
Now, I know how to deal with this in SQL, with either a correlated sub-
select or an even more complicated left outer join. I've forced the
first technique into ActiveRecord wrapping, which isn't fun. Far from
being any help. ARec gets in the way. I've dabbled with ARel which was
even worse, but may be due to my inexperience with it.
Currently, the nicest solution I can think of is to accept the SQL and
go native: i.e., define a view in the database and a read-only model on
top of it.
I appreciate any suggestions how to do this *elegantly* in ARec.
Michael
[*] 2010-06-20, ActiveRecord and ARel: correlated subqueries?
--
Michael Schuerig
mailto:mich...@schuerig.de
http://www.schuerig.de/michael/
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