简单的未定义方法错误 - Rails

Question

我可能忽略了一些简单的东西，但我仍然没能找到问题所在。

控制器：（第一行是一个很长的 Thinking Sphinx 查询）

@artwork_q = Artwork.search params[:q], :conditions => {:subject => params[:artwork][:subject_ids], :location => params[:artwork][:location_ids], :artist_last => params[:artwork][:artist_id], :artist_first => params[:artwork][:artist_id]}, :order => params[:sort][:title]
@last_artwork = Artwork.new
@last_artwork = @artwork_q.last
render 'index2'

查看：

<% @artwork_q.each.with_index do |art, index| %>
    <div class="a-result<%= " last-one" if art.id == @last_artwork.id %>" id="<%= index %>">
<% end %>

我测试了 art.id 并且工作正常。引发错误的是 @last_artwork.id：

NoMethodError in Artworks#index2
Showing /Users/<user>/Developer/<project>/<rails_root>/app/views/artworks/index2.html.erb where line #49 raised:

undefined method `id' for nil:NilClass

感谢您的帮助！

Answer 1

[].last => nil 即您的查询 returns 没有结果。在遍历它们之前，只需检查 @artwork_q 是否有一些结果。

<% unless @artwork_q.blank? %>
  <% @artwork_q.each.with_index do |art, index| %>
    <div class="a-result<%= " last-one" if art.id == @last_artwork.id %>" id="<%= index %>">
  <% end %>
<% end %>

Answer 2

试试这个：

<% unless @artwork_q.blank? %>
  <% @artwork_q.each.with_index do |art, index| %>
    <% unless @last_artwork.blank? %>
      <div class="a-result<%= " last-one" if art.id == @last_artwork.id %>" id="<%= index %>">
      <% end %>
  <% end %>
<% end %>

简单的未定义方法错误 - Rails

Simple Undefined Method Error - Rails

ruby-on-rails

null

each

instance-variables

enumerable