Rails: HTML e-mail containing reference to a S3 hosted image handled by attachment_fu results in nil object error

I'm attempting to send out an HTML e-mail containing a photo (handled by attachment_fu) hosted on Amazon S3 following the submission of an entry.

I keep receiving a nil object error when I try referencing the photo of an entry in ActionMailer. Here's the relevant code ...

class Entry < ActiveRecord::Base

  include AASM

  aasm_initial_state :new

  aasm_state :new
  aasm_state :pending
  aasm_state :rejected, :enter => :reject_entry
  aasm_state :approved, :enter => :approve_entry
  aasm_state :archived
  aasm_state :deleted

  has_one :photo, :dependent => :destroy

  ...

  aasm_event :pending do
    transitions :to => :pending, :from => [:new], :guard => 'process_new_entry'
  end

  ...

  def process_new_entry
    self.make_approval_code
    EntryMailer.deliver_pending_entry_notification(self)
  end
  ...
end

As you can see above the entry transitions through states using AASM. I don't think my issue is due to AASM events, but I'm putting it out there in case.

class Photo < ActiveRecord::Base

  belongs_to :entry

  has_attachment  :content_type => 'image/jpeg',
                  :storage => :s3,
                  :expires_in => 48.hours.to_i,
                  :processor=> :Rmagick,     # attachment_fu looks in this order: ImageScience, Rmagick, MiniMagick
                  :min_size => 1.megabyte,
                  :max_size => 5.megabytes,
                  :thumbnails => { 
                    :medium => '632',
                    :thumb => 'c117x117'
                  }
...
end

In my ActionMailer I have the following:

class EntryMailer < ActionMailer::Base

  helper :entries

  def pending_entry_notification(entry)
    setup_email(entry)
    @content_type = "text/html"
    ...
    @body[:photo_url] = entry.photo.authenticated_s3_url(:thumb)
  end
  ...
end

I end up receiving the following error:

You have a nil object when you didn't expect it!
T开发者_高级运维he error occurred while evaluating nil.authenticated_s3_url

I can successfully get everything else about the entry (including other associations), but trying to reference entry.photo fails.

Any ideas?

it looks like entry.photo is returning nil which would be the case if that particular entry did not have a photo associated with it.

You need to check entry.photo before trying to call authenticated_s3_url(:thumb) on it.

@body[:photo_url] = entry.photo.authenticated_s3_url(:thumb) if entry.photo

or some variation might work (ymmv, I did not test that)

It turns out my entry object is stale when the mailer fires off. Reloading the object prior to triggering the mailer solved the problem.

class Entry < ActiveRecord::Base
  ...

  def process_new_entry
    self.make_approval_code
    self.reload
    EntryMailer.deliver_pending_entry_notification(self)
  end
  ...
end