rails 使用sort_by方法根据数组里面的某个属性进行排序，但是这个属性有空值

Question

<% issues.sort_by{|u| u.due_date}.each do |issue| %>
<%= render partial: 'tree_node', :locals => {:issue => issue, :query => query, :issues_ids => issues_ids} %>
<% end %>
上面的代码中u.due_date有空值，
报的错误是：
ActionView::Template::Error (comparison of NilClass with Date failed):
22: <% end %>
23:
24:
25:

26: <% issues.sort_by{|u| u.due_date}.each do |issue| %>
27: <%# issues.each do |issue| %>
28: <%= render partial: 'tree_node', :locals => {:issue => issue, :query => query, :issues_ids => issues_ids} %>
请教一下各位大神，有什么好的解决方案吗，既按照due_date排序，又解决due_date有空值的问题。

Answer 1

https://stackoverflow.com/questions/808318/sorting-a-ruby-array-of-objects-by-an-attribute-that-could-be-nil