example: sitemap for this site

routes.rb

get '/sitemap', to: 'sitemap#index'

sitemap.controller.rb

class SitemapController < ApplicationController
  def index
    render content_type: "application/xml"
  end
end

views/layouts/sitemap.html.erb

<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
  <%= yield %>
</urlset>

views/sitemap/index.html.erb

<url>
  <loc><%= 'https://zguillez.tips' %></loc>
  <lastmod><%= Date.today.to_s %></lastmod>
  <changefreq>weekly</changefreq>
  <priority>1</priority>
</url>
<% Category.all.each do |cat| %>
    <url>
      <loc><%= 'https://zguillez.tips/' + cat.slug %></loc>
      <lastmod><%= cat.updated_at.strftime("%Y-%m-%d") %></lastmod>
      <changefreq>monthly</changefreq>
      <priority>0.8</priority>
    </url>
<% end %>
<% Tip.all.each do |tip| %>
    <url>
      <loc><%= 'https://zguillez.tips/' + tip.category.slug + '/' + tip.slug %></loc>
      <lastmod><%= tip.updated_at.strftime("%Y-%m-%d") %></lastmod>
      <changefreq>yearly</changefreq>
      <priority>0.5</priority>
    </url>
<% end %>