Multi step form / wizard responses for Ajax (modals) and HTML requests.

_javascript_response.js.erb

<% message = flash[:notice] || flash[:alert] %>
<% flash.delete(:notice); flash.delete(:alert) %>
<% alert = message.present? ? "alert('#{message}');" : '' %>

<% if <a href="/path">@path</a>.present? %>
  $.ajax({ url: "<%= @path %>", data: <%= raw @data.to_json %>, type: "<%= @method.to_s.upcase %>", dataType: "script"}).done(function(data) {
    eval(data);
    <%= raw alert %>
  })
  .fail(function(data) {
    <%= raw alert %>
    alert("Failed to load <%= @path %>!");
  });
<% elsif @template.present? %>
  <% if @template_format == 'html' %>
    <% if @target_is_modal %>
      $(@target).html("<%= escape_javascript(
        render(
          partial: 'shared/layouts/twitter_bootstrap/modal', 
          locals: { title: @modal_title, body: render(template: "#{controller_name}/#{@template}.html") }
        ) 
      ) %>");
    <% else %>
      $("<%= @target %>").html("<%= escape_javascript render(template: "#{controller_name}/#{@template}.html") %>");
    <% end %>
  <% elsif @template_format == 'js' %>
    <%= render template: "#{controller_name}/#{@template}.js" %>
  <% end %>
  <%= raw alert %>
<% elsif message.present? %>
  <%= raw alert %>
<% end %>

_twitter_bootstrap_modal_layout.html.erb

<% body ||= nil %>
<% footer ||= nil %>
<div class="modal-header">
  <button type="button" id="close_bootstrap_modal_button" class="close" data-dismiss="modal" aria-hidden="true">&times;</button>
  <h3><%= title %></h3>
</div>
<div class="modal-body" style="overflow-y:none;">
  <%= body || yield(:modal_body) %>
</div>
<div class="modal-footer">
  <%= footer || yield(:modal_footer) %>
</div>

application_controller.rb

class ApplicationController < ActionController::Base
  private
  
  def render_or_redirect_by_request_type
      if request.xhr? || request.env['HTTP_X_REQUESTED_WITH'] == 'XMLHttpRequest'
        render_modal_javascript_response
      elsif @template.present?
        render @template
      elsif @path.present?
        redirect_to @path
      end
    end
  
  def render_javascript_response
    @method ||= :get
    @data ||= {}
    @template ||= action_name unless <a href="/path">@path</a>.present?
    @template_format ||= 'html'
    @target ||= "#bootstrap_modal"
    @target_is_modal = @target_is_modal.nil? ? true : @target_is_modal
    @modal_title ||= I18n.t("#{controller_name}.#{action_name}.title")
  
    render partial: 'shared/javascript_response.js', layout: false
  end
end

your_rails_controller.rb

class YourRailsController < ApplicationController
  def your_ajax_and_html_action
    render_or_redirect_by_request_type
  end
end