How to add flash message in Rails 4

_flash_messages.html.erb

<% flash.each do |type, message| %>
  <div class="alert <%= bootstrap_class_for(type) %> alert-dismissable fade in">
    <button type="button" class="close" data-dismiss="alert" aria-hidden="true">&times;</button>
    <%= message %>
  </div>
<% end %>

application.html.erb

<%= render partial: "shared/flash_messages", flash: flash %> 

application_helper.rb

module ApplicationHelper

  def bootstrap_class_for flash_type
    case flash_type
      when :success
        "alert-success" # Green
      when :error
        "alert-danger" # Red
      when :alert
        "alert-warning" # Yellow
      when :notice
        "alert-info" # Blue
      else
        flash_type.to_s
    end
  end

end