t.belongs_to in migration

reference http://stackoverflow.com/questions/9471091/t-belongs-to-in-migration

auto create  *_id , *_type
       # Adds a reference. Optionally adds a +type+ column, if <tt>:polymorphic</tt> option is provided.

      # <tt>references</tt> and <tt>belongs_to</tt> are acceptable.

      # ===== Examples

      #  t.references(:goat)

      #  t.references(:goat, :polymorphic => true)

      #  t.belongs_to(:goat)

      def references(*args)

        options = args.extract_options!

        polymorphic = options.delete(:polymorphic)

        args.each do |col|

          @base.add_column(@table_name, "#{col}_id", :integer, options)

          @base.add_column(@table_name, "#{col}_type", :string, polymorphic.is_a?(Hash) ? polymorphic : options) unless polymorphic.nil?

        end

      end

      alias :belongs_to :references

Polymorphic Associations

rails data-method changed by javascript

reference http://stackoverflow.com/questions/9935956/changing-data-method-with-javascript-does-not-change-what-method-the-ajax-calls

$(this).data('method', 'post'); # sets "data-method" attribute to "post"
$(this).data('method', 'delete'); # sets "data-method" attribute to "delete"

For example, given the following HTML:
<div data-role="page" data-last-value="43" data-hidden="true" data-options='{"name":"John"}'></div>

All of the following jQuery code will work.

$( "div" ).data( "role" ) === "page";



$( "div" ).data( "lastValue" ) === 43;



$( "div" ).data( "hidden" ) === true;



$( "div" ).data( "options" ).name === "John";

好用工具-偵測系統環境nmon for Linux

http://sourceforge.net/projects/nmon/postdownload?source=dlp

http://sourceforge.net/projects/nmon/?source=pdlp

監控好工具

nmon_x86_64_rhel6

Page Caching - rails 3

Source : http://railscasts.com/episodes/89-page-caching-revised?view=asciicast

Page caching is one of the most efficient forms of caching  in Rails app

1.
enable perform_caching

development.rb

config.action_controller.perform_caching = true

2.
add page caching to the actions we want to cache

class ProductsController < ApplicationController

  

  caches_page :index, :show

  

  def index

    @products = Product.page(params[:page]).per_page(5)

  end



  def show

    @product = Product.find(params[:id])

  end



.....

3.
then , refresh the page , we will find in the folder "public" , it auto create a file named "product.html" contains the full response for the /products page

4.
one issue we will have is that any URL parameters we pass are ignored .
so include the page as part of the URL path instead of as a query parameter

get 'products/page/:page', to: 'products#index'

5.cache expiration
when the content of the cache changes , we will need to flush the cache

    expire_page products_path

    expire_page product_path(product)

    expire_page "/"

    FileUtils.rm_rf "#{page_cache_directory}/products/page"

6.Flash message is stored in the cache , so it's shown everytime
   we need a way to hide these when we're caching the page

  before_filter(only: [:index, :show]) { @page_caching = true }  

<%= csrf_meta_tag unless @page_caching %>

<% unless @page_caching %>

                <% flash.each do |name, msg| %>

            <%= content_tag :div, msg, id: "flash_#{name}" %>

          <% end %>