如何在 rails 邮件程序预览中获取 request.host？

Question

Awesome: rails now offers a way to preview mailer views using a class that inherits from

 ActionMailer::Preview

Rails seems to be using this controller to set all this magic up:

Rails::MailersController#preview

Unfortunately, my app is multi-tenant, and my mailers rely on the request.host being passed to them so that they are styled according to the domain that they were triggered from.

I would love to be able to key off of the url in in the address bar when setting up may mailer previews. I'm having to do strange things to get this working (partly because I'm creating feature specs for these too), but mostly because I have to set up my mailers in a context that does not have access to the request object, even though my mailers need it to work properly.

class SiteMailerPreview < ActionMailer::Preview
  def support_email_notification
    support_email = SupportEmail.first
    SiteMailer.support_email_notification(support_email, request).deliver
  end

  private

  def request
    request = Struct.new(:host).new
    request.host = 'local.myhost.net'
    request
  end
end

Currently the host is set statically so I can't really test the mailers against multiple hosts.

Answer 1

request will not be available in models and mailers. The only way that can enable you to access request in a model or mailer is to pass the request from controller . Check the below example:

class BooksController < ApplicationController
  def create
    book = Book.create(title: 'xyz', author: current_user)
    BookMailer.new_book_added(book.id, request).deliver
  end
end

and the mailer may look like below:

class BookMailer < ActionMailer::Base
     def new_book_added(book_id, request)
        @book = Book.find book_id
        @url  = books_url(@book, host: request.host_with_port )
        mail(:to => @book.author.email,
             :subject => "Your book is published")
     end
end

and since you mentioned your app is multitenant and assuming you're using apartment gem, You can use Apartment::Tenant.current which will give you the subdomain .

Answer 2

In rails 5.2 you have ActiveSupport::CurrentAttributes available, from the docs:

Abstract super class that provides a thread-isolated attributes singleton, which resets automatically before and after each request. This allows you to keep all the per-request attributes easily available to the whole system.

I currently use it in my app to store request specific things that I need anywhere (even models, mailers, decorators etc. It has been super useful. Using ActiveSupport::CurrentAttributes if set up correctly would allow to do things like:

Current.request

This is the set up that I have in my app:

In my models

#models/current.rb
class Current < ActiveSupport::CurrentAttributes
  attribute :request_id, :user_agent, :ip_address, :user, :request
end

Controllers concerns:

#controllers/set_current_request_details.rb
module SetCurrentRequestDetails
  extend ActiveSupport::Concern

  included do
    before_action do
      Current.request_id = request.uuid
      Current.user_agent = request.user_agent
      Current.ip_address = request.ip
      Current.request = request
    end
  end
end

Controllers:

#controllers/application_controller.rb
class ApplicationController < ActionController::Base
  include SetCurrentRequestDetails

...

Source: https://api.rubyonrails.org/v5.2/classes/ActiveSupport/CurrentAttributes.html