Question

I have the following relationships:

Category has_many :posts
Post has_many :comments
Post has_many :commenters, :through => :comments

I have the following eager load, giving me posts, comments and commenters (note that I need all 3, and hence the includes as opposed to joins)

category.posts.includes(:comments, :commenters)

However, I’d like to limit comments (and if possible commenters) to only those created in the past two weeks while still returning the same set of posts. Initially I thought I could specify a condition on the includes:

category.posts.includes(:comments, :commenters).where("comments.created_at > ?", 2.weeks.ago)

But found that this returns only the posts that meet the condition. I’m thinking that I may need to do something like performing a subquery on comments and then performing a join. Is there an easy way to do this with AR of would I be better off doing this with sql?

Answer 1

Finally managed to figure this out from reading this page:
http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html

I simply needed to create an association in my Post model like:

Post has_many :recent_comments, :class_name = 'Comment', :conditions => ["created_at > ?", 2.weeks.ago]

Then I could do the following to get the desired ActiveRecord::Association object:

category.posts.includes(:recent_comments => :commenters)

There was also a suggestion of doing this by using a scope on a model. However, I read somewhere (I think it was on SO) that scopes are on their way out and that ARel has taken their place so I decided to do this without scopes.