ActionMailer在仅API模式的RoR应用程序中可以正常工作。但是预览无法正常工作。当我打开本地路径时 http://localhost:3001/rails/mailers/
我得到一个空白页。请参阅下面的控制台日志。
我该怎么做才能使预览正常工作？ API模式中可能缺少一些模块吗？
Rails 5.2.3，Ruby 2.6.0，Puma。
Started GET "/rails/mailers/" for 127.0.0.1 at 2019-05-14 17:38:35 +0200
Processing by Rails::MailersController#index as HTML
Rendering /Users/fcandi/.rbenv/versions/2.6.0/lib/ruby/gems/2.6.0/gems/railties-5.2.3/lib/rails/templates/rails/mailers/index.html.erb within layouts/application
Rendered /Users/fcandi/.rbenv/versions/2.6.0/lib/ruby/gems/2.6.0/gems/railties-5.2.3/lib/rails/templates/rails/mailers/index.html.erb within layouts/application (0.4ms)
Completed 200 OK in 3ms (Views: 1.8ms | ActiveRecord: 0.0ms)