Pass multiple objects into action mailer/email contents in rails - ruby-on-rails

Question

Would like to find out how to pass multiple objects into action mailer/email contents in rails. I have no issues passing in #announcement, but not sure how to pass in #post and also #user info.
announcement_controllers.rb
def create
#post = Post.find_by slug: params[:post_id]
#announcement = #post.announcements.build(announcement_params)
#announcement.creator = current_user
if #announcement.save
flash[:notice] = 'Your announcement was created.'
AnnouncementMailer.announcement_alert(#announcement, #post).deliver
redirect_to :back
else
flash[:notice] = 'Unable to create announcement. Make sure you have enter information.'
redirect_to :back
end
end
announcement_mailer.rb
class AnnouncementMailer < ActionMailer::Base
binding.pry
default to: Proc.new { Signup.where(post_id: #post.id, user_id: current_user.id).pluck(:email) },
from: "#{#post.slug}#fundspace.announcement.com"
def announcement_alert(announcement, post)
#announcement = announcement
#post = post
mail(subject: "#{#post.slug}: #{#announcement.title}")
end
end
binding.pry
1: class AnnouncementMailer < ActionMailer::Base
=> 2: binding.pry
3: default to: Proc.new { Signup.where(post_id: #post.id, user_id: current_user.id).pluck(:email) },
4: from: "#{#post.slug}#fundspace.announcement.com"
5:
6: def announcement_alert(announcement, post)
7: #announcement = announcement
[1] pry(AnnouncementMailer)> #post
=> nil
[2] pry(AnnouncementMailer)> #announcement
=> nil
[3] pry(AnnouncementMailer)> #user
=> nil
binding.pry to check on #post in announcement_mailer.rb returns nil. Not sure why. Thanks in advance.

Answer 1

This is a classic case of your debug code giving you the wrong impression. 😃 Your #post is getting passed in fine - but it's happening after the call to binding.pry.
You pass in your post to announcement_alert, which sets it as an instance variable. If you updated that method to look like this, you should see it set fine:
def announcement_alert(announcement, post)
#announcement = announcement
#post = post
binding.pry
mail(subject: "#{#post.slug}: #{#announcement.title}")
end
(You're not checking that post is an object in your mailer, so it's possible for other code to pass nil. That shouldn't be a problem in this case, though - Post.find_by will return nil if there are no matches, but your #post.announcements.build would fail if it had.)
This confusion over where #post gets set is going to cause problems in your default line, too. Statements outside of a method - like your binding.pry and your default to: - get run when the class is evaluated. Statements inside a method - those inside def announcement_alert - don't run until that method is called. And, as we saw above, #post isn't defined until you call announcement_method.
Here's your current default statement:
default to: Proc.new { Signup.where(post_id: #post.id, user_id: current_user.id).pluck(:email) },
from: "#{#post.slug}#fundspace.announcement.com"
Your to: parameter is set to a Proc, which is great - even though it references #post, because it's a Proc it doesn't run until it's needed. You'll have set #post at that point.
Your from: parameter, on the other hand, is just a string. It's outside of a proc. As a result, it tries to evaluate #post.slug immediately - and there's no #post set yet, leading to an error. Changing it to this fixes it:
default to: Proc.new { Signup.where(post_id: #post.id, user_id: current_user.id).pluck(:email) },
from: Proc.new { "#{#post.slug}#fundspace.announcement.com" }