Question

I’m trying to create a Rails 3 model scope, which is, essentially:

scope :published, where(:published => true)

scope :viewable_by, lambda { |user| where(:user_id => user.id).or(published) }

The trouble is, I can’t find a way to make this work.

I had hoped arel_table would work, but it complains it “Cannot visit ActiveRecord::Relation”:

where(arel_table[:user_id].eq(user.id)).or(published)

This could be done by replicating the “published” scope as Arel but then I would be repeating code (and in my project the “published” scope is quite a bit more in depth).

The best I can come up with is this:

scope :viewable_by, lambda { |user| where("(user_id = ?) OR (#{published.where_values.collect(&:to_sql).join(" AND ")})", user.id) }

Answer 1

This is the shortest I could come up with after a bit of digging around:

scope :published, where(:published => true)
scope :viewable_by, lambda { |user| where("user_id = ? OR #{published.where_clauses.first}", user.id) }

(Of course it only works with a single where clause; use a join if there’s more than one.)

I would recommend using a gem like MetaWhere that more clearly exposes some of the Arel underpinnings. Here’s an example from the main page linked above that creates an OR query:

Article.where(:title.matches % 'Hello%' | :title.matches % 'Goodbye%').to_sql
 => SELECT "articles".* FROM "articles" WHERE (("articles"."title" LIKE 'Hello%'
    OR "articles"."title" LIKE 'Goodbye%'))