rails 3 undefined方法`+'代表nil：NilClass

Question

我在rails中制作一个排序表并收到错误。 这是我的index.html.erb

<table>  
  <tr>  
    <th><%= sortable "name" %></th>
    <th><%= sortable "city" %></th>
    <th><%= sortable "country" %></th>
    <th><%= sortable "street_address" %></th>
    <th><%= sortable "sector" %></th>
    <th><%= sortable "telephone" %></th>
    <th><%= sortable "fax" %></th>
  </tr>  

  <% for company in @companies %>  
  <tr>  
    <td><%= company.name %></td>
    <td><%= company.city %></td>
    <td><%= company.country %></td>
    <td><%= company.street_address %></td>
    <td><%= company.sector %></td>
    <td><%= company.telephone %></td>
    <td><%= company.fax %></td>
  </tr>
  <% end %>
</table>

这是我的companies_controller

def index
  @companies = Company.order(params[:sort] + ' ' + params[:direction])
end

这是我的application_helper

def sortable(column, title = nil)  
    title ||= column.titleize  
    direction = (column == params[:sort] && params[:direction] == "asc") ? "desc" : "asc"  
    link_to title, :sort => column, :direction => direction  
end

错误是：

NoMethodError in CompaniesController#index

undefined method `+' for nil:NilClass
app/controllers/companies_controller.rb:21:in `index'

有什么问题，我该如何解决？

Answer 1

你的params[:sort]返回nil 。

你可以通过检查你的参数来修复它：

@companies = Company.scoped
if params[:sort].present? && params[:direction].present?
  @companies = @companies.order(params[:sort] + ' ' + params[:direction])
end

Answer 2

你的params[:sort]是nil ，所以你最好这样做：

def index
  @companies = params[:sort].blank? || params[:direction].blank? ? Company.scoped : Company.order(params[:sort] + ' ' + params[:direction])
end