Rails - May 2009 - ordering by join table - is this possible?

Hey all


Suppose Post has many comments.

Is it possible to call Post.all and order them by the number of
comments each has without adding a column ''comments_count'' to
the Post
table?

If not, can anyone think of a nicer way of doing it this than:

def Post.order_by_comments
  posts = Post.all
  post_hash = {}
  posts.each { |post| post_hash[post.id] = post.comments.count }
  sorted_posts = posts.sort {|a,b| a[1]<=>b[1] }  # =>sorts by keys
  ids = sorted_posts.collect(&:first)  # => collects the post ids
  ids.reverse! # =>sorts the ids from most comments to least
end

^^ I should add

Is it possible to do this in one SQL query?

Thanks

On May 1, 4:55 pm, Gavin
<ga...-YMj/zd8x6QpKMzDMP321V2ksYUyLi9NM@public.gmane.org>
wrote:
> Hey all
>
> Suppose Post has many comments.
>
> Is it possible to call Post.all and order them by the number of
> comments each has without adding a column
''comments_count'' to the Post
> table?
>
> If not, can anyone think of a nicer way of doing it this than:
>
> def Post.order_by_comments
>   posts = Post.all
>   post_hash = {}
>   posts.each { |post| post_hash[post.id] = post.comments.count }
>   sorted_posts = posts.sort {|a,b| a[1]<=>b[1] }  # =>sorts by
keys
>   ids = sorted_posts.collect(&:first)  # => collects the post ids
>   ids.reverse! # =>sorts the ids from most comments to least
> end