Rails配置ActionMailer触发uninitialized constant ActionMailer错误求助

我在配置ActionMailer，使用生成邮件器后的默认代码，现在碰到了uninitialized constant ActionMailer错误，相关代码和错误信息如下：

代码 #

class ApplicationMailer < ActionMailer::Base
  default from: 'from@example.com'
  layout 'mailer'
end

错误栈 #

uninitialized constant ActionMailer
[98c7cc1a-bc46-4d7c-864e-0fc062867062] /Users/priya/fs-statuspage-api/app/mailers/application_mailer.rb:1:in `<main>'
/Users/priya/.rvm/gems/ruby-3.2.0@fs-statuspage-api/gems/bootsnap-1.16.0/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:32:in `require'
/Users/priya/.rvm/gems/ruby-3.2.0@fs-statuspage-api/gems/bootsnap-1.16.0/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:32:in `require'
/Users/priya/.rvm/rubies/ruby-3.2.0/lib/ruby/gems/3.2.0/gems/zeitwerk-2.6.6/lib/zeitwerk/kernel.rb:30:in `require'
/Users/priya/fs-statuspage-api/app/mailers/subscriber_mailer.rb:1:in `<main>'
/Users/priya/.rvm/gems/ruby-3.2.0@fs-statuspage-api/gems/bootsnap-1.16.0/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:32:in `require'
/Users/priya/.rvm/gems/ruby-3.2.0@fs-statuspage-api/gems/bootsnap-1.16.0/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:32:in `require'
/Users/priya/.rvm/rubies/ruby-3.2.0/lib/ruby/gems/3.2.0/gems/zeitwerk-2.6.6/lib/zeitwerk/kernel.rb:30:in `require'
/Users/priya/fs-statuspage-api/app/controllers/subscribers_controller.rb:20:in `create'
/Users/priya/.rvm/gems/ruby-3.2.0@fs-statuspage-api/gems/actionpack-7.0.4.2/lib/action_controller/metal/basic_implicit_render.rb:6:in `send_action'
/Users/priya/.rvm/gems/ruby-3.2.0@fs-statuspage-api/gems/actionpack-7.0.4.2/lib/abstract_controller/base.rb:215:in `process_action'
/Users/priya/.rvm/gems/ruby-3.2.0@fs-statuspage-api/gems/actionpack-7.0.4.2/lib/action_controller/metal/rendering.rb:53:in `process_action'
/Users/priya/.rvm/gems/ruby-3.2.0@fs-statuspage-api/gems/actionpack-7.0.4.2/lib/abstract_controller/callbacks.rb:234:in `block in process_action'
/Users/priya/.rvm/gems/ruby-3.2.0@fs-statuspage-api/gems/activesupport-7.0.4.2/lib/active_support/callbacks.rb:107:in `run_callbacks'
/Users/priya/.rvm/gems/ruby-3.2.0@fs-statuspage-api/gems/actionpack-7.0.4.2/lib/abstract_controller/callbacks.rb:233:in `process_action'
/Users/priya/.rvm/gems/ruby-3.2.0@fs-statuspage-api/gems/actionpack-7.0.4.2/lib/action_controller/metal/rescue.rb:22:in `process_action'
/Users/priya/.rvm/gems/ruby-3.2.0@fs-statuspage-api/gems/actionpack-7.0.4.2/lib/action_controller/metal/instrumentation.rb:67:in `block in process_action'
/Users/priya/.rvm/gems/ruby-3.2.0@fs-statuspage-api/gems/activesupport-7.0.4.2/lib/active_support/notifications.rb:206:in `block in instrument'
/Users/priya/.rvm/gems/ruby-3.2.0@fs-statuspage-api/gems/activesupport-7.0.4.2/lib/active_support/notifications/instrumenter.rb:24:in `instrument'
/Users/priya/.rvm/gems/ruby-3.2.0@fs-statuspage-api/gems/activesupport-7.0.4.2/lib/active_support/notifications.rb:206:in `instrument'
/Users/priya/.rvm/gems/ruby-3.2.0@fs-statuspage-api/gems/actionpack-7.0.4.2/lib/action_controller/metal/instrumentation.rb:66:in `process_action'
/Users/priya/.rvm/gems/ruby-3.2.0@fs-statuspage-api/gems/actionpack-7.0.4.2/lib/action_controller/metal/params_wrapper.rb:259:in `process_action'

解决方法 #

• 确认actionmailer依赖已安装：检查Gemfile中是否存在gem 'actionmailer'，如果没有就添加进去，再运行bundle install。Rails默认会包含这个依赖，但手动搭建项目或误删时会出现缺失。
• 确保完整加载Rails环境：如果是在非Rails环境（比如单独脚本）调用邮件器，需要在文件开头添加以下代码加载环境：

  require_relative '../config/environment'
  

• 检查Zeitwerk加载配置：错误栈显示Zeitwerk在处理文件加载，确认app/mailers目录在Zeitwerk的加载路径中。Rails默认会自动加载该目录，若手动修改过加载配置，需确保该目录被包含。
• 重启服务器：修改Gemfile或加载配置后，重启Rails服务器，确保新配置生效。

内容的提问来源于stack exchange，提问作者Priya Lorha