Ruby on rails RoR SendGrid配置错误，不允许部署到Heroku；第10章哈特尔

我在教程中对SendGrid进行了这一点配置，搜索了很多答案，但在尝试推送到heroku时仍然出现以下错误：

NameError: undefined local variable or method `auto' for #<SampleApp::Application:0x007f5c8bdaef78>

config/environments.rb中的完整代码：

  config.action_mailer.raise_delivery_errors = true
  config.action_mailer.delivery_method = :smtp
  host = 'gentle-sands-4285.herokuapp.com'
  config.action_mailer.default_url_options = { host: host }
  ActionMailer::Base.smtp_settings = {
    :address        => 'smtp.sendgrid.net',
    :port           => '587',
    :authentication => :plain,
    :user_name      => ENV['SENDGRID_USERNAME'],
    :password       => ENV['SENDGRID_PASSWORD'],
    :domain         => 'heroku.com',
    :enable_starttls_auto => true
  }

---

非常感谢您的帮助，希望对通过本教程学习的其他人有所帮助。

与其将此添加到config/environment.rb文件中，不如尝试将其添加到config/environments/文件夹中。以下是我所做的：

我在config/environments/production.rb中添加了以下内容：

  config.action_mailer.default_url_options = { :host => 'YOUR_APP.herokuapp.com' }

  config.action_mailer.delivery_method = :smtp
  config.action_mailer.perform_deliveries = true
  config.action_mailer.raise_delivery_errors = false
  config.action_mailer.default :charset => "utf-8"

  config.action_mailer.smtp_settings = {
    address: ENV["SMTP_ADDRESS"],
    port: 587,
    domain: ENV["EMAIL_DOMAIN"],
    authentication: "plain",
    enable_starttls_auto: true,
    user_name: ENV["EMAIL_USERNAME"],
    password: ENV["EMAIL_PASSWORD"]
  }

下面是我的config/environments/development.rb：

config.action_mailer.default_url_options = { :host => 'localhost:3000' }
  config.action_mailer.delivery_method = :smtp
  config.action_mailer.smtp_settings = {
    address: ENV["SMTP_ADDRESS"],
    port: 587,
    domain: ENV["EMAIL_DOMAIN"],
    authentication: "plain",
    enable_starttls_auto: true,
    user_name: ENV["EMAIL_USERNAME"],
    password: ENV["EMAIL_PASSWORD"]
  }

config.action_mailer.default_url_options = { :host => 'localhost:3000' }
  config.action_mailer.delivery_method = :smtp
  config.action_mailer.smtp_settings = {
    address: ENV["SMTP_ADDRESS"],
    port: 587,
    domain: ENV["EMAIL_DOMAIN"],
    authentication: "plain",
    enable_starttls_auto: true,
    user_name: ENV["EMAIL_USERNAME"],
    password: ENV["EMAIL_PASSWORD"]
  }