Toastr on Rails

application.html.erb

...

    <% unless flash.empty? %>
      <script type="text/javascript">
        <% flash.each do |name, message| %>
          toastr['<%= flash_for(name) %>']('<%= message %>');
        <% end %>
      </script>
    <% end %>
  </body>
</html>

application_helper.rb

module ApplicationHelper
  FLASH_CLASSES = {
    notice: "success",
    alert: "warning",
    error: "error",
    infod: "info"
  }
  
  def flash_for name
    FLASH_CLASSES[name.to_sym]
  end
  
  ...
end

Toastr on Rails

application.js
`//= require toastr.min`

application.css
`*= require toastr.min`