当作品中没有附件时，下载报错

app/controllers/zipdown_controller.rb

@@ -30,8 +30,7 @@ class ZipdownController < ApplicationController
       if file_count > 0
         zipfile = zip_bid bid
       else
-        render file: 'public/no_file_found.html'
-        return
+        zipfile = {:message => "no file"}
       end
     elsif params[:obj_class] == "HomeworkCommon"
       homework = HomeworkCommon.find params[:obj_id]
@@ -41,8 +40,7 @@ class ZipdownController < ApplicationController
       if file_count > 0
         zipfile = zip_homework_common homework
       else
-        render file: 'public/no_file_found.html'
-        return
+        zipfile = {:message => "no file"}
       end
     else
       logger.error "[ZipDown#assort] ===> #{params[:obj_class]} unKown !!"

public/javascripts/application.js

@@ -901,9 +901,14 @@ $(function(){
     $('#download_homework_attachments').bind('ajax:complete', function (event, data, status, xhr) {
         if(status == 'success'){
             var res = JSON.parse(data.responseText);
-            if(res.length<1){
+            if(res.length == null){
+                alert("该作业没有任何附件可下载");
+            }
+            else if(res.length<1){
                 return;
             }
+            else
+            {
                 if(res.length==1){
                     location.href = '/zipdown/download?file='+res[0].file;return;
                 }
@@ -921,6 +926,7 @@ $(function(){
 
                 }
             }
+        }
     });
 });