Rails | yakjuly's blog

把AJAX操作从controller中移到helper

September 3rd, 2010 yakjuly 2 comments

rails中的ajax操作结合prototype，非常方便。方法也挺简单。

我平常操作ajax的代码喜欢在controller中使用 render :update {|page| … }

但是这样的代码在controller写多了会显得非常肮脏难读。并且，我要对页面进行某个操作，需要在controller中写页面中的dom元素的id等。

例如：

render :update do |page|
  page.replace_html("xxxx", :partial => "xxx")
end

render :update do |page|
   #use alert
   page.alert(@object.errors.full_messages.join(","))
   #or replace notice area
   page.replace_html("error_div", @object.errors.full_messages.join(","))
end

当一次ajax访问需要对页面调用多个动作时，代码就显得乱了。利用rails的helper,我们可以将render:update的block中的内容放到helper中，这为我们复用和重构提供了一个有效的工具。例如：

module ApplicationHelper

  def update_time
    page.alert 'hello'
  end

  def spike
    render(:update){|page| page.alert_hello}
  end
end

另外，把代码移到helper中也可以让这些ajax操作在controller中显得更有意义。

controller：

class User::CommentsController < User::BaseController
  before_filter :prepare_comment

  def index

  end

  def new

    respond_to do |type|
      type.js {
        render :update do |page|
          page.create_comment_form
        end
      }
    end
  end

  def create
    success = @comment.save

    respond_to do |type|
      type.js {
        render :update do |page|
          if success
            page.clear_comment_form
            refresh_comment_list(page)
          else
            page.show_error_messages(@comment)
          end
        end
      }
    end
  end

  def edit
    respond_to do |type|
      type.js {
        render :update do |page|
          page.create_comment_form
        end
      }
    end
  end

  def update
    success = @comment.save
    respond_to do |type|
      type.js {
        render :update do |page|
          if success
            page.clear_comment_form
            refresh_comment_list(page)
          else
            page.show_error_messages(@comment)
          end
        end
      }
    end
  end

  def destroy
    @comment.destroy
    render :nothing => true
  end

  private

  def prepare_comment
    case action_name
    when "new", "create"
      @comment = @user.comments.build(params[:comment])
    when "edit", "update", "destroy"
      @comment = @user.comments.find(params[:id])
      @comment.attributes=(params[:comment])
    when "index"
      @comments = @user.comments
    end
  end

end

接下来 helper

module User::CommentHelper
  def refresh_comment_list(page)
    @comments = @user.comments
    page.replace_html("comment_list", :partial => "list")
  end

  def clear_comment_form
    page.replace_html("edit_comment", "")
  end

  def create_comment_form
    page.replace_html("edit_comment", :partial => "form")
  end

  def comment_form_head
    case params[:action]
    when "new", "create"
      [@comment, {:url => user_comments_path}]
    when "edit", "update"
      [@comment, {:url => user_comment_path(@user, @comment), :html => {:method => :put}}]
    end
  end
end

这里有个缺憾就是 refresh_comment_list方法不能直接写成page.refresh_comment_list

因为在javascript generator中不能读到 @user 这个实例变量。因此只有写成refresh_comment_list(page). 并且helper方法中包含了数据库查询语句。

虽然美中不足，但代码看起来还是舒服多了。

view中还可以重用helper中的部分方法

<% remote_form_for *comment_form_head do |f| %>
<div class="order" style="clear:left">
  <table>
    ........
    <tr><th></th><td><%= submit_tag(t(:submit)) %> <%= link_to_function(t(:cancel), update_page{|page| page.clear_comment_form}) %></td></tr>
  </table>
</div>
<% end %>

经过这样改写后，controller中不用关注 dom对象如何变化，helper与页面中的dom对象关系更加紧密。

Categories: rails, ruby Tags: rails, ruby

rails中的select和include查询

August 2nd, 2010 yakjuly No comments

Rails中ActiveRecord finders不允许我们在include预加载关联对象时使用select。

例如这样的情况：

class Student < ActiveRecord::Base
   has_many :calls
   has_one :call
end

class Call < ActiveRecord::Base
   belongs_to :student
end

希望在显示student时，显示它的最近更新的call的日期。

改善前：

@students = Student.all(:include => [:call])

改善后：

#include eql left outer join
@students = Student.all(:select => "students.id, students.login, students.called_times,
calls.updated_at as last_called_at", :joins => "left outer join calls on students.id = calls.student_id")

Categories: rails, ruby Tags: rails, ruby

rails3 !!! Missing the mysql gem. Add it to your Gemfile: gem ‘mysql’, ’2.8.1′

July 16th, 2010 yakjuly No comments

Rails3中 rake db:create 或 rake db:migrate 时出错

rake aborted!
!!! Missing the mysql gem. Add it to your Gemfile: gem 'mysql', '2.8.1'
/usr/lib/ruby/gems/1.8/gems/activerecord-3.0.0.beta4/lib/active_record/connection_adapters/mysql_adapter.rb:22:in `mysql_connection'

原因：rails3中使用bundler 管理gem，尽管system中包含gem mysql 仍然报错。

解决：找到rails_app_path下的 GemFile。添加 gem ‘mysql’

更多：Rails3:使用bundler管理gems

Categories: rails, ruby Tags: rails, ruby

cache and sweeper in rails

July 8th, 2010 yakjuly No comments

以关键字来分组显示列表，往往因为查询的数据量大，导致页面打开慢。使用cache action可以大大提高速度。

需要通过sweeper监控model的增删改动作，定时清理缓存。

models:

class TagPage < Page
  has_one :extra, :class_name => "TagPageExtra", :autosave => true
end

class TagPageExtra < ActiveRecord::Base
  belongs_to :tag_page
end

TagPage是扩展了以前的代码，对于新增的属性，通过TagPageExtra来处理。

controller:

class TagPagesController < ApplicationController
  caches_action :list

  def list
    @pages = TagPage.all(:select => "pages.id, pages.title, pages.description", :include => [:extra],
: order => "tag_page_extras.position")
  end

end

sweeper:

#文件放在 app/sweepers文件夹下
#并在environment中添加 文件路径
config.load_paths += %W( #{RAILS_ROOT}/app/sweepers )

class TagPageSweeper < ActionController::Caching::Sweeper
  observe TagPage

   def after_create(obj)
    expire_cache_for(obj)
  end

  def after_destroy(obj)
    expire_cache_for(obj)
  end

  def after_update(obj)
    expire_cache_for(obj)
  end

  private
  def expire_cache_for(obj)
    expire_action(list_tag_pages_path)
  end
end

＃注意要在application controller中声明 才会起作用
class ApplicationController < ActionController::Base
  cache_sweeper :tag_page_sweeper
end

view:

<%= t("records_not_found")  if @pages.blank? %>
<dl>
  <% @pages.group_by(&:description).each do |description, pages| %>
  <dt><%= link_to description.nil? ? "<b>null</b>" : "<b>#{description}</b>", tag_pages_path(:tag => description) %></dt>
  <dd>
    <ul>
    <% pages.each do |page| %>
      <li class="tag"><%= link_to page.title, edit_tag_page_path(page) %></li>
    <% end %>
    </ul>
  </dd>
  <% end %>
</dl>

结果：
ProcessingTagPagesController#list (for xxx.xxx.xxx.xxx at 2010-07-08 09:24:03) [GET]
Filter chain halted as [#<ActionController::Filters::AroundFilter:0xb60d27d8 @identifier=nil,
@kind=:filter, @method=#<Proc:0xb79b6ba0@/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.4/lib/action_controller/caching/actions.rb:64>,
@options={:only=>#<Set: {"list"}>, :if=>nil, :unless=>nil}>] did_not_yield.
Completed in 8ms (View: 0, DB: 0) | 200 OK [http://www.xxxx.com/tag_pages/list]
这次直接读取了缓存 DB查询为0.

Categories: rails Tags: rails

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cache and sweeper in rails

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把AJAX操作从controller中移到helper