It would probably at that. Might be better to start thinking about
keeping counts at least cached if not fully handled.
The only thing I worry about is the chance that I or hobo have some
update calls in place that wouldn't trigger an observer.
I worked out a way to do it with SQL but means I have to add an
additional layer of SQL for every ratable model.
raise "Invalid object(s) passed.\n#{user.inspect}\n#
{category.inspect}" unless
user.class == User or category.class == RatingCategory
Rating.connection.select_value("SELECT SUM(rating) FROM " +
"(SELECT DISTINCT ratings.* FROM ratings,pictures,users where "
+
"(ratable_id = pictures.id AND pictures.user_id = #{user.id}) "
+
"and rating_category_id = #{category.id});").to_i
Unfortunately, select_value doesn't do SQL escaping which is somewhat
disconcerting.
On Aug 6, 9:32 pm, Bryan M <[email protected]> wrote:
> Why not add two fields to User, num_ratings and avg_rating, and update
> User with a RatingObserver?
>
> (I hope I'm not talking out my arse, but I think that would work)
>
> On Aug 6, 7:46 pm, kevinpfromnm <[email protected]> wrote:
>
> > Ok, I'll start off with the basic models
> > Rating
> > belongs_to :ratable, :polymorphic => true
>
> > Picture
> > has_many :ratings, :as => :ratable
> > belongs_to :user, :creator => true
>
> > Post
> > has_many :ratings, :as => :ratable
> > belongs_to :user, :creator => true
>
> > I'm wanting to be able to give an average for a user for all ratings
> > applied to their submissions. There will be additional models in the
> > future that are ratable as well.
>
> > So, any ideas on a good way to approach this? There are a couple of
> > simple ways but they won't scale. And this relation will probably be
> > one of the most pushed that I'll have in the app. So, I really need a
> > way to grab the rating for all ratables that belong to a user. From
> > my current sense of things looks like I'm going to have to write some
> > SQL to do it but figured I'd ask anyway in case someone knew of a nice
> > trick to do sums across polymorphic types.
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