Loading ActiveRecord associations by hand

Rails
1

Hello,

I’m having this frustrating problem with AR. I want to load AR
associations by hand. I have the following situation:

  • 2 models: child and parent
  • parent has has_one association to child
  • I have loaded set of parent objects (without children)

Now I want to load parent objects with childrens with only one sql
select.

So I load child objects according to parent ids. Did it with one
select, so that’s fine. But then the troubles begin. Now I want to
dynamically associate (or fill association) every parent object with
corresponding object. So I set it with:
parent.child = child

But that also saves the object, which I do not want. I’ve also tried
with “parent.build_child( child.attributes”, but this is even worse,
as it also destroys existing object before setting it…

So please… can anyone help me, how to load associations by hand?

Many thanks!

Uros

2

On 9 Apr 2008, at 13:33, [email protected] wrote:

select.

So I load child objects according to parent ids. Did it with one
select, so that’s fine. But then the troubles begin. Now I want to
dynamically associate (or fill association) every parent object with
corresponding object. So I set it with:
parent.child = child

This is basically how edge rails handles eager loading, the relevant
bit of code is at
http://dev.rubyonrails.org/browser/trunk/activerecord/lib/active_record/association_preload.rb
(look at the set_association_single_records/
set_association_collection_records methods in particular, don’t forget
to call loaded on the association too)

Fred

3

Thanks for the tip Fred, it worked!

Instead of “parent.child = child”
I’ve used: “parent.set_child_target( child )”

Work like a charm (so far)!