获取未定义的方法`contains_attachment？＆＃39;在文档/附件中使用sunspot_solr进行搜索时

Question

我正在尝试使用sunspot_solr在附件中实现全文搜索，但在运行undefined method contains_attachment?时获取rake sunspot:solr:reindex。

我跟着这个： https://cbpowell.wordpress.com/2012/09/18/indexing-rich-documents-with-rails-sunspot-solr-sunspot-cell-and-carrierwave-cookbook-style/

这是我的Gemfile：

gem 'sunspot', :git => "git://github.com/sunspot/sunspot.git"
gem 'sunspot_solr', :git => "git://github.com/sunspot/sunspot.git"
gem 'sunspot_rails', :git => "git://github.com/sunspot/sunspot.git", :require => "sunspot_rails"
gem 'sunspot_cell', :git => 'git://github.com/zheileman/sunspot_cell.git'
gem 'sunspot_cell_jars'
gem 'progress_bar'

需要帮助!!