Rails nested models with comments as commentable (polymorphic association) - ruby-on-rails

Question

I have question and answer models with the comment to both as commentable. Comments on the question work fine but on the answer I am getting: "undefined method `comments' for nil:NilClass." Following is the code:
controller/comment_controller.rb
class CommentsController < ApplicationController
before_action :authenticate_user!
def create
#comment = #commentable.comments.new comment_params
#comment.user = current_user
#comment.save
redirect_to #commentable, notice: "Thanks for your comment."
end
private
def comment_params
params.require(:comment).permit(:content)
end
end
controller/questions/comment_controller.rb
class Questions::CommentsController < CommentsController
before_action :set_commentable
private
def set_commentable
#commentable = Question.find_by_permalink(params[:question_id])
end
end
controller/questions/answers/comment_controller.rb
class Answers::CommentsController < CommentsController
before_action :set_commentable
private
def set_commentable
#question = Question.find_by_permalink(params[:question_id])
#commentable = #question.answers.find(params[:answer_id])
end
end
Models
class Question < ApplicationRecord
belongs_to :user
has_many :answers, dependent: :destroy
has_many :comments, as: :commentable, dependent: :destroy
end
class Answer < ApplicationRecord
belongs_to :user
belongs_to :question
has_many :comments, as: :commentable, dependent: :destroy
end
class Comment < ApplicationRecord
belongs_to :commentable, polymorphic: true
belongs_to :user
end
Routes:
resources :questions do
resources :comments, module: :questions
resources :answers, :only => [:create, :destroy, :update] do
resources :comments, module: :answers
end end
Question: show.html.erb:
<h1><%= link_to #question.title, question_path(#question)%></h1>
<p><%= #question.description %></p>
<%= render partial: "comments/comments", locals: {commentable: #question } %>
<%= render partial: "comments/form", locals: {commentable: #question } %>
<% #question.answers.each do |answer| %>
<%= render partial: "comments/comments", locals: {commentable: #answer } %>
<%= render partial: "comments/form", locals: {commentable: #answer } %>
<% end %>
_comments.html.erb
<div class="content">
<h2 class="title"><%= pluralize(commentable.comments.count, 'Comment', plural: 'Comments') %></h2>
<% commentable.comments.each do |comment| %>
<small><%= time_ago_in_words(comment.created_at) %></small>
<p><%= comment.content %></p>
<% end %>
</div>
_form.html.erb
<%= form_for [commentable, Comment.new] do |f| %>
<%= f.text_area :content, class:'textarea', placeholder:'Add a comment' %>
<%= f.submit 'Comment', class:'button is-primary' %>
<% end %>
Update:
Strange thing happend. I reset the database and altest I can add comment to the answer now, not sure how it got fixed.
However I am getting a new error which make more sense: undefined method `answer_comments_path' for #<#:0x007f89e04905b8>. I have put <%= answer.inspect %> just before the comment input form to the answer and I am getting as expected answer model data.
So when I do the rake routes i dont see answer_comments_path.
The route is question_answer_comments_path. How can I pass this path to the answer/comments form.