Switching templates with view variants

You can switch to different templates using Rails' support for view variants, which can be used to override the template used inside the controller.

By setting the request.variant option to any value (in this case, :admin) at any point in any controller, you can add a new variant to Rails' template lookup tree (in this case, .html+admin.erb).

For example, to add a button to become the admin to view certain functionality:

class CustomersController < Admin::ApplicationController
  before_action :with_variant, only: %i[index]

  private

  def with_variant
    if @current_user.admin?
      request.variant = :admin
    end
  end
end

<!-- app/views/admin/customers/_index_header.html.erb -->
<p class="identity__banner">
  You are logged in as <em><%= pundit_user.name %></em>.
  <%= link_to("Become the Admin", become_admin_customer_path("admin"),
        class: "identity__become-action")%>
</p>

<!-- app/views/admin/customers/_index_header.html+admin.erb -->
<p class="identity__banner identity__banner--admin">
  You are logged in as <em><%= pundit_user.name %></em>.
</p>