Using class_name in a custom Rails generator

Question

I have a basic custom generator that looks like this, that inherits from Rails::Generators::NamedBase in a Rails 5.1 app

class NotificationGenerator < Rails::Generators::NamedBase
  source_root File.expand_path('../templates', __FILE__)

  def notification
    copy_file "notification.rb", "app/notifications/#{file_name}.rb"
    copy_file "notification_spec.rb", "spec/notifications/#{file_name}_spec.rb"
  end
end

My template file is called notification.rb.tt which lives under the ../templates directory.

The template looks like this:

class <%= class_name %> < Notification

  def to_mail
  end

  def to_sms
  end
end

However when I run the generator the created files have <%= class_name %> in the file rather than the result of that method call. How do I get the generator to actually render like an erb template?

Answer 1

After digging through some Rails core commits I found this issue that discusses the file extension a bit.

It seems like in rails 5.2 all templates got renamed to .tt (which means that the above code might work if I were to upgrade, I did not go that deep into rails core).

However as a fix for my own personal use on 5.1 the last comment by rafaelfranca unveils a solution. If I use 'template' rather than copy_file it parses and outputs correctly.

Working generator looks like this:

class NotificationGenerator < Rails::Generators::NamedBase
  source_root File.expand_path('../templates', __FILE__)

  def notification
    template "notification.rb", "app/notifications/#{file_name}.rb"
    template "notification_spec.rb", "spec/notifications/#{file_name}_spec.rb"
  end
end