ActionController::UrlGenerationError: No route matches {:action=>"show", :controller=>"posts"} - ruby-on-rails

Question

I'm trying to generate sitemap automatically by using a sitemap_generator gem. I tried to add show action since I started getting an error. It was originally empty..
Following is my posts controller:
class PostsController < ApplicationController
before_filter :authorize, only: [:edit, :update, :new, :create, :destroy]
before_filter :find_post, only: [:show, :edit, :update, :destroy]
def index
#posts = Post.order("created_at DESC").page(params[:page]).per(9)
respond_to do |format|
format.html
format.rss { render :layout =>false }
end
end
def show
#posts = Post.all
end
def new
#post = Post.new
end
def create
#post = Post.new(post_params)
if #post.save
redirect_to posts_url
else
render 'new'
end
end
def edit
end
def update
if #post.update_attributes(post_params)
redirect_to post_url(#post), notice: "#{#post.title} Updated"
else
render 'edit'
end
end
def destroy
#post.destroy
redirect_to posts_url, notice: "#{#post.title} Deleted"
end
private
def post_params
params.require(:post).permit(:title, :contents, :author_id, :approved, :summary, :preview_image_id, :category, :social_title, :blog_title)
end
def find_post
#post = Post.friendly.find(params[:id])
# If an old id or a numeric id was used to find the record, then
# the request path will not match the post_path, and we should do
# a 301 redirect that uses the current friendly id.
if params[:action] == 'show' && request.path != post_path(#post)
return redirect_to #post, :status => :moved_permanently
end
end
end
routes.rb
Rails.application.routes.draw do
root to: "home#index"
resources :posts do
resources :comments
end
end
sitemap.rb
Post.friendly.find_each do |post|
add post_url(post), :lastmod => post.created_at
end
I tried both with 'friendly' and without 'friendly'.
and When I run rake sitemap:refresh I receive the following error
ubuntu:~/environment/site (master) $ rake sitemap:refresh
In '/home/ubuntu/environment/site/public/':
Post Load (0.6ms) SELECT "posts".* FROM "posts" ORDER BY "posts"."id" ASC LIMIT 1000
rake aborted!
ActionController::UrlGenerationError: No route matches {:action=>"show", :controller=>"posts", :format=>nil, :id=>nil, :locale=>#<Post id: 1, title: "4 Tips For Managing Your Maintenance Team", contents: "<p>Maintenance teams are a special kind of problem...", approved: nil, created_at: "2020-03-30 16:17:28", updated_at: "2020-05-04 17:07:30", url: nil, blog_title: "4 Tips For Managing Your Maintenance Team">} missing required keys: [:id]