Create local proxy server associated with public url whenever starting rails server in development mode. It uses proxylocal.com service and gem to generate the public url.

proxylocal_initializer.rb

# This initializer creates a local proxy server that makes the local web server accessible
# via a public host generated by ProxyLocal service - http://www.proxylocal.com

Rails.application.config.after_initialize do
  server_running = defined?(WEBrick) || defined?(Rails::Server) || defined?(PhusionPassenger) ? true : false
  next unless Rails.env.development? && server_running

  Thread.new do
    ProxyLocal::Client.run({
      server_host: 'proxylocal.com',
      server_port: '8282',
      local_port: '3000',
      tls: false,
      verbose: false
    })
  end
end

def define_default_rails_public_url(url)
  uri = URI(url)
  Rails.application.routes.default_url_options.merge!(host: uri.host, port: uri.port, protocol: uri.scheme)
end

# Opening ProxyLocal class to capture the public URL
class ProxyLocal::Client
  def receive_message_with_capture(message)
    url = message[/http.*com/]
    define_default_rails_public_url(url) if url

    receive_message_without_capture(message)
  end

  alias_method_chain :receive_message, :capture
end