不允许重复发送。但是发送过程不会给予提示。如果课程或者项目或者组织已经有了该资源，那么该资源的更新时间会变化

app/controllers/users_controller.rb

@@ -1489,6 +1489,16 @@ class UsersController < ApplicationController
       unless course_ids.nil?
         course_ids.each do |id|
           next if ori.blank?
+          @exist = false
+          Course.find(id).attachments.each do |att|  #如果课程中包含该资源
+            if att.id == ori.id || (!att.copy_from.nil? && !ori.copy_from.nil? && att.copy_from == ori.copy_from) || att.copy_from == ori.id || att.id == ori.copy_from
+              att.created_on = Time.now
+              att.save
+              @exist = true
+              break
+            end
+          end
+          next if @exist
           attach_copied_obj = ori.copy
           attach_copied_obj.tag_list.add(ori.tag_list) # tag关联
           attach_copied_obj.container = Course.find(id)
@@ -1515,6 +1525,16 @@ class UsersController < ApplicationController
         unless course_ids.nil?
           course_ids.each do |id|
             next if ori.blank?
+            @exist = false
+            Course.find(id).attachments.each do |att|  #如果课程中包含该资源
+              if att.id == ori.id || (!att.copy_from.nil? && !ori.copy_from.nil? && att.copy_from == ori.copy_from) || att.copy_from == ori.id || att.id == ori.copy_from
+                att.created_on = Time.now
+                att.save
+                @exist = true
+                break
+              end
+            end
+            next if @exist
             attach_copied_obj = ori.copy
             attach_copied_obj.tag_list.add(ori.tag_list) # tag关联
             attach_copied_obj.container = Course.find(id)
@@ -1563,6 +1583,16 @@ class UsersController < ApplicationController
       unless project_ids.nil?
         project_ids.each do |project_id|
           next if ori.blank?
+          @exist = false
+          Project.find(project_id).attachments.each do |att|  #如果课程中包含该资源
+            if att.id == ori.id || (!att.copy_from.nil? && !ori.copy_from.nil? && att.copy_from == ori.copy_from) || att.copy_from == ori.id || att.id == ori.copy_from
+              att.created_on = Time.now
+              att.save
+              @exist = true
+              break
+            end
+          end
+          next if @exist
           attach_copied_obj = ori.copy
           attach_copied_obj.tag_list.add(ori.tag_list) # tag关联
           attach_copied_obj.container = Project.find(project_id)
@@ -1588,6 +1618,16 @@ class UsersController < ApplicationController
         unless project_ids.nil?
           project_ids.each do |project_id|
             next if ori.blank?
+            @exist = false
+            Project.find(project_id).attachments.each do |att|  #如果课程中包含该资源
+              if att.id == ori.id || (!att.copy_from.nil? && !ori.copy_from.nil? && att.copy_from == ori.copy_from) || att.copy_from == ori.id || att.id == ori.copy_from
+                att.created_on = Time.now
+                att.save
+                @exist = true
+                break
+              end
+            end
+            next if @exist
             attach_copied_obj = ori.copy
             attach_copied_obj.tag_list.add(ori.tag_list) # tag关联
             attach_copied_obj.container = Project.find(project_id)
@@ -1633,6 +1673,16 @@ class UsersController < ApplicationController
       ori = Attachment.find_by_id(send_id)
       unless subfield_id.nil?
           attach_copied_obj = ori.copy
+          @exist = false
+          OrgSubfield.find(subfield_id).attachments.each do |att|  #如果课程中包含该资源
+            if att.id == ori.id || (!att.copy_from.nil? && !ori.copy_from.nil? && att.copy_from == ori.copy_from) || att.copy_from == ori.id || att.id == ori.copy_from
+              att.created_on = Time.now
+              att.save
+              @exist = true
+              break
+            end
+          end
+          if @exist == false #如果不存在该资源
             attach_copied_obj.tag_list.add(ori.tag_list) # tag关联
             attach_copied_obj.container = OrgSubfield.find(subfield_id)
             attach_copied_obj.created_on = Time.now
@@ -1644,6 +1694,7 @@ class UsersController < ApplicationController
             end
             attach_copied_obj.save
           end
+      end
     elsif params[:send_ids].present?
       send_ids = params[:send_ids].split(" ")
       subfield_id = params[:subfield]
@@ -1655,6 +1706,16 @@ class UsersController < ApplicationController
         ori = Attachment.find_by_id(send_id)
         unless subfield_id.nil?
             next if ori.blank?
+            @exist = false
+            OrgSubfield.find(subfield_id).attachments.each do |att|  #如果课程中包含该资源
+              if att.id == ori.id || (!att.copy_from.nil? && !ori.copy_from.nil? && att.copy_from == ori.copy_from) || att.copy_from == ori.id || att.id == ori.copy_from
+                att.created_on = Time.now
+                att.save
+                @exist = true
+                break
+              end
+            end
+            next if @exist
             attach_copied_obj = ori.copy
             attach_copied_obj.tag_list.add(ori.tag_list) # tag关联
             attach_copied_obj.container = OrgSubfield.find(subfield_id)