系统消息只显示30天前的

app/helpers/users_helper.rb

@@ -33,6 +33,12 @@ module UsersHelper
     result = unsolved_issues_count + unfinished_homework_count + unfinished_test_count + unfinished_poll_count + anonymous_evaluation_count + unapproval_homework
   end
 
+  # 判断某个时间再多少天前
+  # params[:num] 天数
+  def many_days_ago time, num
+    time > Time.now - 86400 * num
+  end
+
   def issue_list(issues, &block)
     ancestors = []
     issues.each do |issue|

app/views/users/_user_message_system.html.erb

@@ -1,4 +1,4 @@
-<% if ma.class == SystemMessage %>
+<% if ma.class == SystemMessage && many_days_ago(ma.created_at, 30) %>
     <%# @user_system_messages.each do |usm| %>
     <ul class="homepageNewsList fl">
       <div class="longMessageWidth">