未定義的方法`link_url'爲零：NilClass

Question

我是RoR的新手。在運行rails _3.2.13_ s我收到以下錯誤信息：

nishant@nishant-Inspiron-1545:~/voylla_website$ rails _3.2.13_ s 
DEPRECATION WARNING: class_inheritable_attribute is deprecated, please use class_attribute method instead. Notice their behavior are slightly different, so refer to class_attribute documentation first. (called from <top (required)> at /home/nishant/.rvm/gems/ruby-1.9.2-p320@voylla/bundler/gems/spree_active_shipping-a85128c2ddd9/lib/spree_active_shipping.rb:2) 
DEPRECATION WARNING: class_inheritable_attribute is deprecated, please use class_attribute method instead. Notice their behavior are slightly different, so refer to class_attribute documentation first. (called from <top (required)> at /home/nishant/.rvm/gems/ruby-1.9.2-p320@voylla/bundler/gems/spree_active_shipping-a85128c2ddd9/lib/spree_active_shipping.rb:2) 
=> Booting WEBrick 
=> Rails 3.1.10 application starting in development on http://0.0.0.0:3000 
=> Call with -d to detach 
=> Ctrl-C to shutdown server 
/home/nishant/.rvm/gems/ruby-1.9.2-p320@voylla/gems/actionpack-3.1.10/lib/action_dispatch/http/mime_type.rb:101: warning: already initialized constant PDF 
[DEPRECATION WARNING] Nested I18n namespace lookup under "activerecord.attributes.order" is no longer supported 
[2013-09-26 16:11:20] INFO WEBrick 1.3.1 
[2013-09-26 16:11:20] INFO ruby 1.9.2 (2012-04-20) [i686-linux] 
[2013-09-26 16:11:20] INFO WEBrick::HTTPServer#start: pid=17154 port=3000 


Started GET "/" for 127.0.0.1 at 2013-09-26 16:11:46 +0530 
    Processing by HomeController#index as HTML 
    (0.3ms) SHOW search_path 
    ScrollerImage Load (1.2ms) SELECT "scroller_images".* FROM "scroller_images" WHERE "scroller_images"."promotional_content_type" = 'DesignerOfWeek' 
Rendered home/welcome.html.erb within layouts/spree_application (31.3ms) 
Completed 500 Internal Server Error in 422ms 

ActionView::Template::Error (undefined method `link_url' for nil:NilClass): 
    9:   sc = sc[0] unless sc.nil? 
    10:  %> 
    11:  <div class="standby"> 
    12:   <a href="<%= sc.link_url %>"><img src="<%= sc.url.gsub("images","images0") %>" alt="<%= sc.alt_text %>"></a> 
    13:  </div> 
    14:  </div> 
    15: <!-- Featured Collection --> 
    app/views/home/welcome.html.erb:12:in `block in _b2963a3bf824a09e97c143671f39792f' 
    app/views/home/welcome.html.erb:1:in `_b2963a3bf824a09e97c143671f39792f' 
    app/controllers/home_controller_decorator.rb:4:in `index' 

Rendered /home/nishant/.rvm/gems/ruby-1.9.2-p320@voylla/gems/actionpack-3.1.10/lib/action_dispatch/middleware/templates/rescues/_trace.erb (1.8ms) 
Rendered /home/nishant/.rvm/gems/ruby-1.9.2-p320@voylla/gems/actionpack-3.1.10/lib/action_dispatch/middleware/templates/rescues/_request_and_response.erb (1.1ms) 
Rendered /home/nishant/.rvm/gems/ruby-1.9.2-p320@voylla/gems/actionpack-3.1.10/lib/action_dispatch/middleware/templates/rescues/template_error.erb within rescues/layout (6.0ms) 

可能有人請幫助我瞭解和解決這個問題。 感謝

編輯：以下是應用程序/視圖/家/ welcome.html.erb：

<% cache("welcome_page", :expires_in => 1.day) do %> 
<div class="home_page_container"> 
<div class="container_12"> 
    <div class="third_row grid_12"> 
    <!-- Deal of the Day --> 
    <div class="grid_4 dod_grid grids"> 
    <h3><span class="home">Deal of the </span>WEEK</h3> 
     <% sc = ScrollerImage.where(:promotional_content_type => "DesignerOfWeek") 
     sc = sc[0] unless sc.nil? 
     %> 
     <div class="standby"> 
     <a href="<%= sc.link_url %>"><img src="<%= sc.url.gsub("images","images0") %>" alt="<%= sc.alt_text %>"></a> 
     </div> 
    </div> 
    <!-- Featured Collection --> 
    <div class="grid_4 collection_grid grids"> 
    <h3><span class="home">Featured</span> COLLECTION</h3> 
     <% sc = ScrollerImage.where(:promotional_content_type => "FeaturedCollection") 
     sc = sc[0] unless sc.nil? %> 
     <div class="standby"> 
      <a href="<%= sc.link_url %>"><img src="<%= sc.url.gsub("images", "images1") %>" alt="<%= sc.alt_text %>"></a> 
     </div> 
    </div> 

    <!-- Get the Look --> 
    <div class="grid_4 look_grid grids"> 
     <h3><span class="home">Get the</span> LOOK</h3> 
     <% sc = ScrollerImage.where(:promotional_content_type => "GettheLook") 
     sc = sc[0] unless sc.nil? %> 
     <div class="standby"> 
     <a href="<%= sc.link_url %>"><img src="<%= sc.url.gsub("images", "images2") %>" alt="<%= sc.alt_text %>"></a> 
     </div> 
    </div> 
    </div> 
    <br /> 

    <div class="first_row grid_12"> 
    <!-- Tag Grids x 4 --> 
    <h3 class="h3_look"><span class="home">SHOP BY</span> LOOK</h3> 
    <% sc = ScrollerImage.where(:promotional_content_type => "Tag") 
    sc.each_with_index { |x,i| 
    %> 
    <div class="grid_3 tag_grids grids" id="rollover_<%= x.id %>"> 
     <div class="tag_front" id="rollover_<%= x.id %>"> 
     <a href="<%= x.link_url%>"><img src="<%= x.url.gsub("images", "images"+(i%3).to_s) %>" alt="<%= x.alt_text %>" /></a> 
     <div id="rollover_<%=x.id%>" class="tag_rollover" style="visibility: hidden;"> 
     <% rb = rollover_blurb(x.alt_text) %> 
     <a href="<%= x.link_url%>">Over <%= rb[0].to_s %> designs available starting at <%= rb[1].to_s %>.</a> 
     </div> 
    </div> 
    </div> 
    <script> 
    $(document).ready(function(){ 
    $("div.tag_front#rollover_<%= x.id %>").mouseover(function() { 
     var rlid = $(this).attr("id") 
     if ($("div.tag_rollover#"+rlid).css("visibility") != "visible") { 
     $($(this).children()[0]).css("opacity", "0.4"); 
     $("div.tag_rollover#"+rlid).css("visibility", "visible"); 
     } 
    }).mouseout(function() { 
     var rlid = $(this).attr("id") 
     if ($("div.tag_rollover#"+rlid).css("visibility") != "hidden") { 
     $($(this).children()[0]).css("opacity", "1.0"); 
     $("div.tag_rollover#"+rlid).css("visibility", "hidden"); 
     } 
    }); 
    }); 
    </script> 
    <% } %> 
    </div> 

    <br /> 
</div> 
</div> 
<%- content_for(:head) do -%> 
    <meta property="fb:page_id" content="141716202609787" /> 
    <meta name="p:domain_verify" content="8475d705acb964b1874e518347854744"/> 
<%end%> 

<%end%> 

Answer 1

這是誰造成問題的代碼：

sc = ScrollerImage.where(:promotional_content_type => "FeaturedCollection") 
sc = sc[0] unless sc.nil? 

你應該這樣做（假設你想得到第一個結果）：

sc = ScrollerImage.where(:promotional_content_type => "FeaturedCollection").first 
if sc 
    # your code here 
end 

請注意，在視圖中進行查詢是不好的做法。你應該把它們放在你的控制器中或更好，在presenter。