迁移报错

db/migrate/20190622055449_modify_shixun_info_for_shixuns.rb

@@ -11,7 +11,7 @@ class ModifyShixunInfoForShixuns < ActiveRecord::Migration[5.2]
                            evaluate_script: shixun[:evaluate_script], shixun_id: shixun.id)
       end
     end
-    if shixun.description.present?
+    if Shixun.first.description.present?
       remove_columns :shixuns, :description, :propaedeutics, :evaluate_script
     end
   end