preview_enabled = true로 동작 메일러를 4.2에 구성하는 방법

Question

이제 레일 4.2가 릴리스되었으므로 메일러 미리보기를 준비에서 내 프로젝트에 추가하고 싶습니다. 간단이 코드를 넣어 것입니다하지만이 I 다음은 내 staging.rb 파일에

config.action_mailer.preview_enabled = true 
config.action_mailer.preview_path = "#{Rails.root}/lib/mailer_previews" 

을하지만, 나에게 method_missing 오류가 있습니다.

내가 뭘 잘못 했니? 누군가 나를 도울 수 있습니까?

스택 추적 :

method_missing': undefined method `preview_enabled=' for ActionMailer::Base:Class (NoMethodError) 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/actionmailer-4.2.0.rc1/lib/action_mailer/railtie.rb:41:in `block (3 levels) in <class:Railtie>' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/actionmailer-4.2.0.rc1/lib/action_mailer/railtie.rb:41:in `each' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/actionmailer-4.2.0.rc1/lib/action_mailer/railtie.rb:41:in `block (2 levels) in <class:Railtie>' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/activesupport-4.2.0.rc1/lib/active_support/lazy_load_hooks.rb:38:in `instance_eval' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/activesupport-4.2.0.rc1/lib/active_support/lazy_load_hooks.rb:38:in `execute_hook' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/activesupport-4.2.0.rc1/lib/active_support/lazy_load_hooks.rb:45:in `block in run_load_hooks' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/activesupport-4.2.0.rc1/lib/active_support/lazy_load_hooks.rb:44:in `each' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/activesupport-4.2.0.rc1/lib/active_support/lazy_load_hooks.rb:44:in `run_load_hooks' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/actionmailer-4.2.0.rc1/lib/action_mailer/base.rb:945:in `<class:Base>' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/actionmailer-4.2.0.rc1/lib/action_mailer/base.rb:417:in `<module:ActionMailer>' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/actionmailer-4.2.0.rc1/lib/action_mailer/base.rb:9:in `<top (required)>' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/actionmailer-4.2.0.rc1/lib/action_mailer/railtie.rb:59:in `block in <class:Railtie>' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/activesupport-4.2.0.rc1/lib/active_support/lazy_load_hooks.rb:36:in `call' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/activesupport-4.2.0.rc1/lib/active_support/lazy_load_hooks.rb:36:in `execute_hook' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/activesupport-4.2.0.rc1/lib/active_support/lazy_load_hooks.rb:45:in `block in run_load_hooks' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/activesupport-4.2.0.rc1/lib/active_support/lazy_load_hooks.rb:44:in `each' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/activesupport-4.2.0.rc1/lib/active_support/lazy_load_hooks.rb:44:in `run_load_hooks' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/railties-4.2.0.rc1/lib/rails/application/finisher.rb:62:in `block in <module:Finisher>' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/railties-4.2.0.rc1/lib/rails/initializable.rb:30:in `instance_exec' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/railties-4.2.0.rc1/lib/rails/initializable.rb:30:in `run' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/railties-4.2.0.rc1/lib/rails/initializable.rb:55:in `block in run_initializers' 
from /home/vagrant/.rvm/rubies/ruby-2.1.3/lib/ruby/2.1.0/tsort.rb:226:in `block in tsort_each' 
from /home/vagrant/.rvm/rubies/ruby-2.1.3/lib/ruby/2.1.0/tsort.rb:348:in `block (2 levels) in each_strongly_connected_component' 
from /home/vagrant/.rvm/rubies/ruby-2.1.3/lib/ruby/2.1.0/tsort.rb:427:in `each_strongly_connected_component_from' 
from /home/vagrant/.rvm/rubies/ruby-2.1.3/lib/ruby/2.1.0/tsort.rb:347:in `block in each_strongly_connected_component' 
from /home/vagrant/.rvm/rubies/ruby-2.1.3/lib/ruby/2.1.0/tsort.rb:345:in `each' 
from /home/vagrant/.rvm/rubies/ruby-2.1.3/lib/ruby/2.1.0/tsort.rb:345:in `call' 
from /home/vagrant/.rvm/rubies/ruby-2.1.3/lib/ruby/2.1.0/tsort.rb:345:in `each_strongly_connected_component' 
from /home/vagrant/.rvm/rubies/ruby-2.1.3/lib/ruby/2.1.0/tsort.rb:224:in `tsort_each' 
from /home/vagrant/.rvm/rubies/ruby-2.1.3/lib/ruby/2.1.0/tsort.rb:205:in `tsort_each' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/railties-4.2.0.rc1/lib/rails/initializable.rb:54:in `run_initializers' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/railties-4.2.0.rc1/lib/rails/application.rb:352:in `initialize!' 
from /home/vagrant/workspace/bankfacil/communicator/config/environment.rb:5:in `<top (required)>' 
from /home/vagrant/workspace/bankfacil/communicator/config.ru:3:in `require' 
from /home/vagrant/workspace/bankfacil/communicator/config.ru:3:in `block in <main>' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/rack-1.6.0.beta2/lib/rack/builder.rb:55:in `instance_eval' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/rack-1.6.0.beta2/lib/rack/builder.rb:55:in `initialize' 
from /home/vagrant/workspace/bankfacil/communicator/config.ru:in `new' 
from /home/vagrant/workspace/bankfacil/communicator/config.ru:in `<main>' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/rack-1.6.0.beta2/lib/rack/builder.rb:49:in `eval' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/rack-1.6.0.beta2/lib/rack/builder.rb:49:in `new_from_string' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/rack-1.6.0.beta2/lib/rack/builder.rb:40:in `parse_file' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/rack-1.6.0.beta2/lib/rack/server.rb:299:in `build_app_and_options_from_config' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/rack-1.6.0.beta2/lib/rack/server.rb:208:in `app' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/railties-4.2.0.rc1/lib/rails/commands/server.rb:61:in `app' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/rack-1.6.0.beta2/lib/rack/server.rb:336:in `wrapped_app' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/railties-4.2.0.rc1/lib/rails/commands/server.rb:139:in `log_to_stdout' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/railties-4.2.0.rc1/lib/rails/commands/server.rb:78:in `start' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/railties-4.2.0.rc1/lib/rails/commands/commands_tasks.rb:80:in `block in server' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/railties-4.2.0.rc1/lib/rails/commands/commands_tasks.rb:75:in `tap' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/railties-4.2.0.rc1/lib/rails/commands/commands_tasks.rb:75:in `server' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/railties-4.2.0.rc1/lib/rails/commands/commands_tasks.rb:39:in `run_command!' 
from /home/vagrant/.rvm/gems/ruby-2.1.3/gems/railties-4.2.0.rc1/lib/rails/commands.rb:17:in `<top (required)>' 
from bin/rails:4:in `require' 
from bin/rails:4:in `<main>' 

Answer 1

그것은, staging.rb에서, 단지 다음과 같이 대신 preview_enabled의 show_previews를 추가 할 작품 :

config.consider_all_requests_local = true 

# mailer previews 
config.action_mailer.show_previews = true 
config.action_mailer.preview_path = "#{Rails.root}/lib/mailer_previews"