Challenge 1: A Basic Job — Solution

# app/jobs/resize_image_job.rb
class ResizeImageJob < ApplicationJob
  queue_as :default

  def perform(image_id)
    image = Image.find(image_id)
    image.resize!
  end
end

# app/controllers/images_controller.rb
def create
  @image = Image.create!(image_params)
  ResizeImageJob.perform_later(@image.id)
  redirect_to @image
end

=begin
Notes:
- perform(image_id) takes the ID, not the Image object itself -- by the time
  a worker actually picks this job up, the object built in the controller is
  long gone; looking the record up fresh inside perform guarantees current
  data instead of a stale in-memory snapshot.
- Image.find(image_id) raises ActiveRecord::RecordNotFound on its own if the
  image was deleted before the job ran, which is exactly the failure
  Challenge 2's discard_on is meant to handle.
- perform_later enqueues and returns immediately -- the create action's
  redirect_to @image fires right away, without waiting for the resize to
  actually happen.
=end