首页时间排序，可能会引起其他调用event_datetime的问题。待观察

app/controllers/messages_controller.rb

@@ -79,6 +79,7 @@ class MessagesController < ApplicationController
     @reply.board = @board
     @reply.safe_attributes = params[:reply]
     @topic.children << @reply
+    @topic.update_attribute(:updated_on, Time.now)
     if !@reply.new_record?
       call_hook(:controller_messages_reply_after_save, { :params => params, :message => @reply})
       attachments = Attachment.attach_files(@reply, params[:attachments])

app/helpers/welcome_helper.rb

@@ -102,10 +102,21 @@ module WelcomeHelper
   end
 
   def find_new_forum_topics limit=7
-    Memo.where('memos.parent_id IS NULL').reorder('memos.created_at DESC').limit(limit)
+    # Memo.where('memos.parent_id IS NULL').reorder('memos.created_at DESC').limit(limit)
     # activity = Redmine::Activity::Fetcher.new(nil)
     # activity.scope=['memos']
     # activity.events_welcome(nil, nil, {:limit => limit})
+
+    # resultSet = Memo.where('memos.parent_id IS NULL').includes(:last_reply).order('COALESCE (last_replies_memos.created_at, memos.created_at) DESC').limit(limit)
+    # resultSet += Message.where('messages.parent_id IS NULL').includes(:last_reply).order('COALESCE (last_replies_messages.created_on, messages.created_on) DESC').limit(limit)
+    resultSet = Memo.where('parent_id IS NULL').order('updated_at DESC').limit(limit)
+    resultSet += Message.where('parent_id IS NULL').order('updated_on DESC').limit(limit)
+    # resultSet = resultSet.to_a
+    resultSet.sort! {|x,y| y.event_datetime <=> x.event_datetime}
+    # for i in 0..(resultSet.size-1)
+    #   resultSet[i] = resultSet[i].parent if resultSet[i].parent
+    # end
+    resultSet.take(limit)
   end
 
   private

app/models/forum.rb

@@ -1,6 +1,6 @@
 class Forum < ActiveRecord::Base
   include Redmine::SafeAttributes
-  has_many :topics, :class_name => 'Memo', :conditions => "#{Memo.table_name}.parent_id IS NULL", :order => "#{Memo.table_name}.created_at DESC"
+  has_many :topics, :class_name => 'Memo', :conditions => "#{Memo.table_name}.parent_id IS NULL", :order => "#{Memo.table_name}.created_at DESC", :dependent => :destroy
   has_many :memos, :dependent => :destroy
   belongs_to :creator, :class_name => "User", :foreign_key => 'creator_id' 
   safe_attributes 'name',

app/models/memo.rb

@@ -17,7 +17,8 @@ class Memo < ActiveRecord::Base
 	# 					#:project_key => "#{Forum.table_name}.project_id"
 	# 					:date_column => "#{table_name}.created_at"
 	acts_as_event :title => Proc.new {|o| "#{o.forum.name}: #{o.subject}"},
-				  :datetime => :created_at,
+				  :datetime => :updated_at,
+				  # :datetime => :created_at,
 				  :description => :content,
 				  :author => :author,
 				  :type => Proc.new {|o| o.parent_id.nil? ? 'Memo' : 'Reply'},

app/models/message.rb

@@ -33,6 +33,7 @@ class Message < ActiveRecord::Base
                      :date_column => "#{table_name}.created_on"
   acts_as_event :title => Proc.new {|o| "#{o.board.name}: #{o.subject}"},
                 :description => :content,
+                :datetime => :updated_on,
                 # :datetime => "#{Message.table_name}.created_on",
                 :group => :parent,
                 :type => Proc.new {|o| o.parent_id.nil? ? 'message' : 'reply'},