nil:NilClass 的未定义方法“comment”（ruby on rails）

Question

In Ruby on Rails I'm trying to render a JSON file that will map each comment to a review. Each review has many comments but each comment belongs to a review.

Here is my controller to generate a JSON file:

 reviews: @ship.reviews.preload(:user_profile).map do |review|
        {
          id: review.id,
          body: review.body,
          rating: review.rating,
          user_profile: review.user_profile,
          comments: @review.comments.preload(:comment).map do |comment|
            {
              id: comment.id,
              body: comment.body,
              user_profile: comment.user_profile_id,
            }
          end
        }

Here is the comment model:

class Comment < ApplicationRecord
  belongs_to :user_profile
  belongs_to :review
end

Here is the review.rb model:

class Review < ApplicationRecord
  belongs_to :user_profile
  belongs_to :ship
  has_many :comments
  has_many :helpfuls
end

However my JSON file returns an error:

undefined method `comment' for nil:NilClass

on this line:

comments: @review.comment.preload(:comment).map do |comment|

Answer 1

Remove .preload(:commment) from @review.comments.preload(:comment).map do |comment| . You don't need it at all.