Решено Flash-сообщение для формы Rails, работающей через AJAX

<%= link_to "blablabla", users_path, remote: true %>

class UsersController < ApplicationController
  def index
    # do some things here
    respond_to do |format|
      format.js { flash.now[:notice] = "Here is my flash notice" }
    end
  end
end

$("#flash").html('<%= j render partial: "shared/notice_banner" %>');

<div id="flash">
  <% if notice.present? %>
    <%= render partial: "shared/notice_banner" %>
  <% end %>
</div>

<div data-alert class="alert-box">
  <%= notice %>
  <a href="#" class="close">&times;</a>
</div>

-    var $flash = $('<div class="alert alert-'+options.type+' fade in"><button type="button" class="close" data-dismiss="alert">&times;</button>'+message+'</div>');
+    var $flash = $('<div class="alert alert-'+options.type+' fade show"><button type="button" class="close" data-dismiss="alert">&times;</button>'+message+'</div>');

module ApplicationHelper
  def bootstrap_class_for_flash(flash_type)
    case flash_type
    when 'success'
      'alert-success'
    when 'error'
      'alert-danger'
    when 'warning'
      'alert-warning'
    when 'notice'
      'alert-info'
    else
      flash_type.to_s
    end
  end
end

<div class="container">
  <% flash.each do |type, msg| %>
    <div class="alert <%= bootstrap_class_for_flash(type) %> alert-dismissable fade show">
      <%= msg %>
    </div>
  <% end %> 
</div>

<%= render partial: 'flash', flash: flash %>