👀 Views: 398 💬 Answers: 1 📅 Created: 2025-06-12

ruby rails activerecord polymorphic Ruby

I'm working on a Rails 6.1 application where I'm trying to fetch associated records using polymorphic associations, but I'm working with unexpected nil values in my queries. I have two models, `Comment` and `Post`, where `Comment` can belong to either a `Post` or a `Image`. Here's the relevant part of my model setup: ```ruby class Comment < ApplicationRecord belongs_to :commentable, polymorphic: true end class Post < ApplicationRecord has_many :comments, as: :commentable end class Image < ApplicationRecord has_many :comments, as: :commentable end ``` When I try to load comments for a specific post, I use the following query: ```ruby post = Post.find(post_id) comments = post.comments.includes(:commentable) ``` However, `comments` returns an array containing instances of `Comment`, but `commentable` on some of them is `nil`. I checked the database and confirmed that the corresponding entries in the `comments` table have valid `commentable_id` and `commentable_type` values. Here’s an example of what I see: ```ruby comments.each do |comment| puts comment.commentable.inspect end ``` This outputs `nil` for some comments, even though they have valid foreign keys. To troubleshoot, I tried to run the query directly in the console: ```ruby Comment.where(commentable_type: 'Post', commentable_id: post.id).includes(:commentable) ``` This still yields the same results with some `nil` values. I wonder if there's a specific configuration or something else I'm missing that could cause this behavior. Are there any known issues with polymorphic associations in Rails 6.1 that could lead to this kind of question? Any guidance would be appreciated!