Render partial在Ruby中，rails上的集合是乘法项 [英] Render partial in Ruby on rails a collection is multiplying items

问题描述

我想在Ruby-on-Rails中显示页面中的项目列表。我在我的 index.html.erb 文件中使用partials

I want to display a list of items in a page in Ruby-on-Rails. I use partials

我有：

<%= @lista = News.find(:all, :order => Document::COL_DATE + ' DESC, id DESC')
    render :partial => "newsitem",
           :layout => "list_news",
           :spacer_template => "spacer",
           :collection => @lista
%>

在 _list_news.html.erb ：

<div class="news">
  <%= yield %>
</div>

在 _spacer.html.erb < hr />

在 _newsitem.html.erb 我有

<%= newsitem_counter + 1 %>
<!-- Code to print details for one item -->

问题是它多次打印列表：

The problem is that it prints the list multiple times:

如果列表有3个项目，它会显示它们3次：1,2,3,1,2,3,1,2,3。

如果它有7个项目，那些项目已打印7次。

If the list has 3 items, it shows them 3 times: 1,2,3,1,2,3,1,2,3.
If it has 7 items, those items are printed 7 times.

我的代码有什么问题？

推荐答案

：layout选项通常与：action或单个：partial，不与：collection集合使用。问题：正在为列表中的每个项目调用yield。

The :layout option is usually used with :action or a single :partial, not with :collection's. The problem: yield is being called for every item in the list.

您必须查看源代码来找出原因：layout和：collection办法;但足以说你的代码应该可能只是重写，以便它不依赖于：layout和：collection一起工作。

You'd have to look at the sources to figure out why :layout and :collection are acting this way; but suffice it to say your code should probably just be rewritten so that it doesn't rely on :layout and :collection working together.

这里有一种方法，假设在其他视图中重用此代码是高优先级。除非你使用大量的缓存，渲染每个部分往往是相当慢，尤其是如果你的news_feed有很多项目，所以我把它整合成一个。

Here's one way you could do so, with the assumption that reusing this code in other views is a high priority. Unless you're using lots of caching, rendering each partial tends to be fairly slow, especially if your news_feed has many items, so I've consolidated it into one.

controller / news_controller.rb

class NewsController < ApplicationController
   def index
     @news_feed = News.find(:all, 
                            :order => Document::COL_DATE + ' DESC, id DESC')
   end
end

views / news / index.html.erb

<%= render :partial => "news_feed",
       :locals => { :news_feed => @news_feed} %>

views / news / _news_feed.html.erb

<ul class="news">
  <% news_feed.each_with_index do |news_item, news_item_counter| %>
     <li>
       <%= newsitem_counter + 1 %>
      <%# Code to print details for one item %>
     </li>
  <% end %>
</ul>

如果呈现一大堆分数对于运行时间来说是好的，你可能会发现这个实现 views / news / _news_feed.html.erb 更好：

If rendering a whole bunch of partials is okay for you running-time wise, you might find this implementation of views/news/_news_feed.html.erb nicer:

<div class="news">
  <%= render :partial => 'news_item', :collection => news_feed, :spacer_template => "horizontal_break" %> 
</div>

views / news / _news_item.html.erb

<%= newsitem_counter + 1 %>
<%# Code to print details for one item %>

views / news / _horizo​​ntal_break.html.erb

< hr />

因此，不是渲染：layout，你渲染一个大的部分，它包装集合。

So instead of rendering :layout, you render one big partial which wraps the collection.

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