Dynamic Finders and Count

rubyonrails-talk
1

Hi!

I have a (hopefully) simple problem, but just don't get the idea how to implement it in rails.

There are two classes, one for users and one for comments. A user has_many comments and each comment belongs_to user.

I tried to do something like this:

@foo = User.find(:all, :order => 'comments_count')

comments_count is not known. An :include => 'comments' also doesn't help (even that the SQL Syntax is doing a join now).

How can I find all Users sorted by the number of comments they have posted? It's enough if the resulting list only contains the count- field as result. It is not necessary to have all comments "attached" to the list.

Thanks in advance!   Markus

2

Off the top of my head, something like this will do the job User.find :all, :select => 'users.*, count(*) as comment_count',     :joins => 'inner join comments on comments.id = comment_id',     :group => 'users.id',                  :order => 'comment_count'

Fred

3

lordbyte wrote:

I tried to do something like this:

@foo = User.find(:all, :order => 'comments_count')

comments_count is not known. An :include => 'comments' also doesn't help (even that the SQL Syntax is doing a join now).

There is no column named comments_count therefore the problem you are getting. What you *could* do is use a counter cache. Then your query would work as is.

Eric

4

Hi!

There is no column named comments_count therefore the problem you are getting. What you *could* do is use a counter cache. Then your query would work as is.

That's great - exactly what I searched! :slight_smile:

Thanks for help!   Markus