ActiveRecord - querying polymorphic associations

Question

I am using polymorphic associations to track Comments in my project. All very straight forward stuff.

The problem I have is in querying based on the polymorphic asso

Answer 1

Checked to work under Rails 5:

Solution 1:

@comments = Comment
              .where(commentable_type: "ForumTopic")
              .joins("INNER JOIN forum_topics ON comments.commentable_id = forum_topics.id")
              .where(forum_topics: {featured: true})
              .all

or

Solution 2:

@comments = Comment
              .joins("INNER JOIN forum_topics ON comments.commentable_id = forum_topics.id AND comments.commentable_type = 'ForumTopic'")
              .where(forum_topics: {featured: true}).all

Pay attention to the raw SQL syntax: no backticks are allowed. See http://guides.rubyonrails.org/active_record_querying.html#joining-tables .

I personally prefer Solution 1 as it contains fewer raw SQL syntax.