Enumerable flash messages in Rails

_flash.html.erb

<% flash.now[:alert] = 'This an example alert message.' %>
<% flash.now[:error] = 'This an example error message.' %>
<% flash.now[:notice] = 'This an example notice message.' %>
<% flash.now[:success] = 'This an example success message.' %>

<% flash.now[:secret] = 'This will not be shown.' %>
<% flash.now[:cool] = true %>

<% flash_messages.each do |type, message| %>
  <div class="flash-<%= type %>"><%= message %></div>
<% end %>

application_controller.rb

class ApplicationController < ActionController::Base
  protect_from_forgery with: :exception

  concerning :Flash do
    included do
      add_flash_types :error, :success
      helper_method :flash_messages
    end

    def flash_messages
      Hash[self.class._flash_types.map { |type| [type, send(type)] }]
    end
  end
end