Render partial in Ruby on rails a collection is multiplying items

问题

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

in my index.html.erb file I have:

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

in _list_news.html.erb I have:

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

in _spacer.html.erb I have <hr/>

in _newsitem.html.erb I have

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

The problem is that it prints the list multiple times:

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.

What is wrong in my code?

回答1:

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.

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.

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>

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/_horizontal_break.html.erb

<hr />

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

回答2:

This is a known problem in Rails 2.3.8 and Rails 3! https://rails.lighthouseapp.com/projects/8994/tickets/2279-render-layout-with-block-and-multiple-yields

来源：https://stackoverflow.com/questions/2209879/render-partial-in-ruby-on-rails-a-collection-is-multiplying-items

标签

ruby-on-rails

collections

renderpartial