Loading ActiveRecord associations by hand

rubyonrails-talk
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

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

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)!