修改获取所有消息的排序算法，使用数据库的order

app/controllers/users_controller.rb

@@ -112,17 +112,10 @@ class UsersController < ApplicationController
     case params[:type]
       when nil
         @message_alls = []
-        system_message_types = MessageAll.where("message_type =?", "SystemMessage").order("created_at desc")
-        messages = MessageAll.where("user_id =? and message_type !=?" ,@user, "SystemMessage").order("created_at desc")
+        messages = MessageAll.where("(user_id =? and message_type !=?) or message_type =?" ,@user, "SystemMessage", "SystemMessage").order("created_at desc")
         messages.each do |message_all|
           @message_alls << message_all.message
         end
-        # 系统消息需要给每个人发送，之所以这样做，可以避免遍历系统所有用户
-        system_message_types.each do |system_message_type|
-          @message_alls << system_message_type.message
-        end
-        # 取出所有符合条件的按照创建时间排序
-        @message_alls = @message_alls.sort {|a,b| b.created_at <=> a.created_at}
       when 'unviewed'
         @message_alls = []
         messages = MessageAll.where("user_id =?", @user).order("created_at desc")