comment.user.username not working on show.html.erb - ruby-on-rails

Question

i'mtrying a simple feature where a user can comment on inquest post , but comment .user.username is not working ,it's rendering comment.user but does not support user attributes
create_table "comments", force: :cascade do |t|
t.string "content"
t.integer "inquest_id"
t.integer "user_id", null: false
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.index ["inquest_id"], name: "index_comments_on_inquest_id"
t.index ["user_id"], name: "index_comments_on_user_id"
end
comment_model
class Comment < ApplicationRecord
belongs_to :inquest
belongs_to :user
end
user_model is simple with has many comments association
comments create method of controller
def create
#comment = Comment.new(comment_params)
pp comment_params
#inquest = Inquest.find(params[:inquest_id])
#comment = Comment.new(comment_params)
#comment.inquest = #inquest
#comment.user = current_user
respond_to do |format|
if #comment.save
format.js do
#inquest = Inquest.find(params[:inquest_id])
end
else
format.html { render :new, status: :unprocessable_entity }
format.json { render json: #comment.errors, status: :unprocessable_entity }
end
end
end
I'm rendering comments in inquest's show.html.erb
Showing /Users/zunairaihsan/Desktop/fyp_ed_bolt/app/views/inquests/show.html.erb
where line #123 raised:
undefined method `user_name' for nil:NilClass
I've tried most of the ways possible , but it's not working.please let me know where I'm wrong

Answer 1

I assume, in inquests/show.html.erb you're displaying multiple comments, something like
<%= #inquest.comments.each do |comment| %>
<%= comment.user.user_name %>
<%= comment.content %>
<% end %>
Many comments will render without issue. Comment model and database doesn't allow user_id to be nil.
But looks like one comment's user_id doesn't have a corresponding id in users table. When you try to figure out what's going on and remove user_name
<%= #inquest.comments.each do |comment| %>
<%= comment.user %>
<%= comment.content %>
<% end %>
Sneaky broken comment probably doesn't show you anything, comment.user is nil, and because you have no validation on comment.content it could also be nil.
First, get rid of comments without user to verify this is the issue:
# this is fast enough for a few thousand comments
>> Comment.find_each { |comment| comment.destroy unless comment.user }
After this inquests/show.html.erb should be working.
To make sure this doesn't happen again:
class User
# this will delete all `user.comments` when you destroy `user`
has_many :comments, dependent: :destroy
# ...
end
To really make sure this doesn't happen again:
class CreateComment < ActiveRecord::Migration[7.0]
def change
create_table :comments do |t|
t.references :user, null: false, foreign_key: true
# ...
end
end
end
With foreign_key constraint, your database will not let you destroy a user if they have comments. This works in tandem with dependent: :destroy. If you delete a user and rails automatically destroys all user.comments, then database will not complain.
Probably do the same for inquest as well if it's not optional.
Also comments without content are not really comments:
class Comment < ApplicationRecord
belongs_to :inquest
belongs_to :user
validates :content, presence: true
end