未定义的方法`＆gt;＆＃39;对于nil：NilClass使用＆time; time_ago_in_words＆＃39;在Rails中

Question

我在尝试使用＆＃39; time_ago_in_words＆＃39;时遇到了一个奇怪的错误。在rails中的conversation.messages.first（created_at）上运行：

<% conversations.each do |conversation| %>
  <% user_status = current_user.id == conversation.sender.id ? conversation.recipient : conversation.sender %>
  <li>
    <%= gravatar_for(user_status, size: 50) %>
    <%= link_to user_status.email, conversation_messages_path(conversation),
        remote: true,
        class: "conversation-names #{'current-link' if conversation == conversations.first}" %>
    <span class="delete-message"><%= link_to do %><i class="fa fa-times"></i><% end %></span>
    <p><%= truncate(conversation.messages.first.try(:body)) %><%= time_ago_in_words conversation.messages.first.try(:created_at) %></p>
  </li>
<% end %>

未定义的方法`＆gt;＆＃39;为零：NilClass。

Answer 1

Iceman击中了头部。

在<li> conversation.message中确保.first存在之前，先致电.first;否则nil将返回SELECT COUNT(DISTINCT pets.id),locations.attr -> 'country' as country FROM pets,photos,locations WHERE photos.pet_id = pets.id AND photos.location_id = locations.id GROUP BY pets.id,locations.attr -> 'country'; 。