Question

I have models called User, Activity, and Task and I can do the following

> puts Activity.joins(:task).to_sql
SELECT "activities".* FROM "activities" INNER JOIN "tasks" ON "tasks"."id" = "activities"."task_id" ORDER BY date DESC

> puts User.first.shared_tasks.to_sql
SELECT "tasks".* FROM "tasks" INNER JOIN "user_tasks" ON "tasks"."id" = "user_tasks"."task_id" WHERE "user_tasks"."user_id" = 1

But when I try to merge the two, I get an array:

> puts Activity.joins(:task).merge(User.first.shared_tasks).to_sql
NoMethodError: undefined method `to_sql' for []:Array

Why is that not returning a relation? I need to put a where clause on it.

Update:

Upon further inspection, it looks likes User.first.shared_tasks is being evaluated to an array of tasks immediately. I can gett the behavior I want by adding an order call:

> puts Activity.joins(:task).merge(User.first.shared_tasks.order()).to_sql
SELECT "activities".* FROM "activities" INNER JOIN "tasks" ON "tasks"."id" = "activities"."task_id" INNER JOIN "user_tasks" ON "tasks"."id" = "user_tasks"."task_id" WHERE "user_tasks"."user_id" = 1 ORDER BY date DESC

Is there a better way to prevent that relation from being evaluated besides adding an empty order?

Answer 1

Alright, I still have not figured out why User.first.shared_tasks is being immediately evaluated, but I have figured out a work around. I can just call scoped:

> User.first.shared_tasks.class
=> Array

> User.first.shared_tasks.scoped.class
=> ActiveRecord::Relation

Now when I try to do the merge:

Activity.joins(:task).merge(User.first.shared_tasks.scoped)

It uses ActiveRecord::Relation#merge instead of Array#merge