我已更新到rails 4.2。当我跟进弃用警告并在我的环境中设置config.active_record.raise_in_transactional_callbacks = true时，我开始遇到问题：
Failure/Error: Unable to find matching line from backtrace
NoMethodError:
undefined method `id' for nil:NilClass
id指的是current_user.id，它已变得不可用（因此错误跟踪中的warden和devise提及）。
删除config.active_record.raise_in_transactional_callbacks = true时，弃用警告仅针对使用回形针的两个模型出现，这让我相信这可能是回形针回调的问题。我可以忽略弃用警告，但我宁愿修复潜在的问题。有什么建议吗？
这是一个错误跟踪：
commpleted 500 Internal Server Error in 152ms
Unexpected error while processing request: undefined method `env' for nil:NilClass
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/Users/j/.rvm/gems/ruby-2.1.2/gems/actionpack-4.2.0/lib/abstract_controller/helpers.rb:67:in `current_user'
/Users/j/Google Drive/rails_projects/versneller/app/views/sync/messages/_message.html.erb:48:in `_app_views_sync_messages__message_html_erb___1152654597097292680_70140856995020'
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/Users/j/Google Drive/rails_projects/versneller/app/controllers/instances_controller.rb:74:in `advice'
/Users/j/.rvm/gems/ruby-2.1.2/gems/actionpack-4.2.0/lib/action_controller/metal/implicit_render.rb:4:in `send_action'
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/Users/j/.rvm/gems/ruby-2.1.2/gems/actionpack-4.2.0/lib/abstract_controller/callbacks.rb:20:in `block in process_action'
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/Users/j/.rvm/gems/ruby-2.1.2/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:288:in `block (2 levels) in halting_and_conditional'
/Users/j/.rvm/gems/ruby-2.1.2/gems/sync-0.3.5/lib/sync/controller_helpers.rb:22:in `block in enable_sync'
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/Users/j/.rvm/gems/ruby-2.1.2/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:427:in `block in make_lambda'
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/Users/j/.rvm/gems/ruby-2.1.2/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:169:in `call'
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/Users/j/.rvm/gems/ruby-2.1.2/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:169:in `call'
/Users/j/.rvm/gems/ruby-2.1.2/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:169:in `block in halting'
/Users/j/.rvm/gems/ruby-2.1.2/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:169:in `call'
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/Users/j/.rvm/gems/ruby-2.1.2/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:169:in `block in halting'
/Users/j/.rvm/gems/ruby-2.1.2/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:169:in `call'
/Users/j/.rvm/gems/ruby-2.1.2/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:169:in `block in halting'
/Users/j/.rvm/gems/ruby-2.1.2/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:151:in `call'
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/Users/j/.rvm/gems/ruby-2.1.2/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:234:in `call'
/Users/j/.rvm/gems/ruby-2.1.2/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:234:in `block in halting'
/Users/j/.rvm/gems/ruby-2.1.2/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:169:in `call'
/Users/j/.rvm/gems/ruby-2.1.2/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:169:in `block in halting'
/Users/j/.rvm/gems/ruby-2.1.2/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:169:in `call'
/Users/j/.rvm/gems/ruby-2.1.2/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:169:in `block in halting'
/Users/j/.rvm/gems/ruby-2.1.2/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:169:in `call'
/Users/j/.rvm/gems/ruby-2.1.2/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:169:in `block in halting'
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/Users/j/.rvm/gems/ruby-2.1.2/gems/thin-1.6.3/lib/thin/connection.rb:84:in `catch'
/Users/j/.rvm/gems/ruby-2.1.2/gems/thin-1.6.3/lib/thin/connection.rb:84:in `pre_process'
/Users/j/.rvm/gems/ruby-2.1.2/gems/thin-1.6.3/lib/thin/connection.rb:53:in `process'
/Users/j/.rvm/gems/ruby-2.1.2/gems/thin-1.6.3/lib/thin/connection.rb:39:in `receive_data'
/Users/j/.rvm/gems/ruby-2.1.2/gems/eventmachine-1.0.7/lib/eventmachine.rb:187:in `run_machine'
/Users/j/.rvm/gems/ruby-2.1.2/gems/eventmachine-1.0.7/lib/eventmachine.rb:187:in `run'
/Users/j/.rvm/gems/ruby-2.1.2/gems/thin-1.6.3/lib/thin/backends/base.rb:73:in `start'
/Users/j/.rvm/gems/ruby-2.1.2/gems/thin-1.6.3/lib/thin/server.rb:162:in `start'
/Users/j/.rvm/gems/ruby-2.1.2/gems/rack-1.6.0/lib/rack/handler/thin.rb:19:in `run'
/Users/j/.rvm/gems/ruby-2.1.2/gems/rack-1.6.0/lib/rack/server.rb:286:in `start'
/Users/j/.rvm/gems/ruby-2.1.2/gems/railties-4.2.0/lib/rails/commands/server.rb:80:in `start'
/Users/j/.rvm/gems/ruby-2.1.2/gems/railties-4.2.0/lib/rails/commands/commands_tasks.rb:80:in `block in server'
/Users/j/.rvm/gems/ruby-2.1.2/gems/railties-4.2.0/lib/rails/commands/commands_tasks.rb:75:in `tap'
/Users/j/.rvm/gems/ruby-2.1.2/gems/railties-4.2.0/lib/rails/commands/commands_tasks.rb:75:in `server'
/Users/j/.rvm/gems/ruby-2.1.2/gems/railties-4.2.0/lib/rails/commands/commands_tasks.rb:39:in `run_command!'
/Users/j/.rvm/gems/ruby-2.1.2/gems/railties-4.2.0/lib/rails/commands.rb:17:in `<top (required)>'
bin/railre'
答案 0 :(得分：0)
以下是您所说的问题：https://github.com/thoughtbot/paperclip/issues/1933（尤其是我的评论：https://github.com/thoughtbot/paperclip/issues/1933#issuecomment-169607838和https://github.com/thoughtbot/paperclip/issues/1933#issuecomment-170509222）
请注意，此警告不是错误，它只会告诉您ActiveRecord的未来行为，这不是浅层错误。
删除config.active_record.raise_in_transactional_callbacks = true会向您显示after_commit / after_rollback的警告并切换到旧行为，这会导致错误。