module Rails::Generators::Actions

def route(routing_code, namespace: nil)

route "root 'admin#index'", namespace: :admin
route "root 'welcome#index'"

Make an entry in Rails routing file config/routes.rb
def route(routing_code, namespace: nil)
  namespace = Array(namespace)
  namespace_pattern = route_namespace_pattern(namespace)
  routing_code = namespace.reverse.reduce(routing_code) do |code, name|
    "namespace :#{name} do\n#{rebase_indentation(code, 2)}end"
  end
  log :route, routing_code
  in_root do
    if namespace_match = match_file("config/routes.rb", namespace_pattern)
      base_indent, *, existing_block_indent = namespace_match.captures.compact.map(&:length)
      existing_line_pattern = /^[ ]{,#{existing_block_indent}}\S.+\n?/
      routing_code = rebase_indentation(routing_code, base_indent + 2).gsub(existing_line_pattern, "")
      namespace_pattern = /#{Regexp.escape namespace_match.to_s}/
    end
    inject_into_file "config/routes.rb", routing_code, after: namespace_pattern, verbose: false, force: false
    if behavior == :revoke && namespace.any? && namespace_match
      empty_block_pattern = /(#{namespace_pattern})((?:\s*end\n){1,#{namespace.size}})/
      gsub_file "config/routes.rb", empty_block_pattern, verbose: false, force: true do |matched|
        beginning, ending = empty_block_pattern.match(matched).captures
        ending.sub!(/\A\s*end\n/, "") while !ending.empty? && beginning.sub!(/^[ ]*namespace .+ do\n\s*\z/, "")
        beginning + ending
      end
    end
  end
end