Rails: passing objects between model and controller - ruby-on-rails

Question

Is there a best practice for managing objects between model and controller in Rails? I've got code that clumsily hands files from controller to model and back like so:
In document_controller.rb:
tmp_file = Tempfile.new(Digest::MD5.hexdigest(rand(12).to_s))
pdf = Prawn::Document.generate(tmp_file.path(), :page_size => "A4", :skip_page_creation => true) do |posting|
#document.process(posting)
send_data posting.render, :filename => "#{#document.id}", :type => "application/pdf"
end
And in document.rb:
def process(pdf)
pdf.start_new_page
pdf.image self.user.logo.path, :width => pdf.bounds.width
pdf.fill_color '#444444'
pdf.image self.component.image_snapshot.path, :width => pdf.bounds.width
pdf.move_down 20
pdf.indent 20 do
pdf.text self.component.name, :size => 24
end
box_start = pdf.cursor
pdf.reflow_column_box([20, box_start-15], :width => pdf.bounds.width-20) do
format_for_prawn(pdf, self.component.body, self.user.colour1)
end
end
How can I rewrite this code so I don't have to clumsily pass the pdf/posting object around? It feels very un-Rails-like.
Thanks for your input.
EDIT: worse example.
Again in the controller:
tempfile = Magick::Image.read(#document.component.image_newsletter.path).first
overlay = Magick::Image.read(#document.user.logo.path).first.resize_to_fit(tempfile.columns)
rec = Magick::Draw.new
rec.stroke = "##{#document.user.colour1}"
rec.fill = "##{#document.user.colour1}"
rec.rectangle 0, 0, tempfile.columns, 5
lank = tempfile.extent(tempfile.columns, tempfile.rows+overlay.rows, 0 ,0)
final = lank.composite(overlay, Magick::SouthGravity, 0, 0, Magick::OverCompositeOp)
rec.draw(final)
send_data final.to_blob, :filename => "#{#document.user.name}-#{#document.id}.jpg", :type => "image/jpg"
This is in the controller because otherwise send_data can't access final. Any help?
Thanks again.

Answer 1

EDIT
You can create extension methods for inbuilt Class by
#lib/ext/prawn/document.rb
class Prawn::Document
def process(pdf)
pdf = self if pdf.blank?
pdf.start_new_page
pdf.image self.user.logo.path, :width => pdf.bounds.width
pdf.fill_color '#444444'
pdf.image self.component.image_snapshot.path, :width => pdf.bounds.width
pdf.move_down 20
pdf.indent 20 do
pdf.text self.component.name, :size => 24
end
box_start = pdf.cursor
pdf.reflow_column_box([20, box_start-15], :width => pdf.bounds.width-20) do
format_for_prawn(pdf, self.component.body, self.user.colour1)
end
end
end
And in your controller
tmp_file = Tempfile.new(Digest::MD5.hexdigest(rand(12).to_s))
pdf = Prawn::Document.generate(tmp_file.path(), :page_size => "A4", :skip_page_creation => true) do |posting|
posting.process
send_data posting.render, :filename => "#{#document.id}", :type => "application/pdf"
end
To load this class, you will need to require it in your config/application.rb file or in an initializer.
require 'ext/prawn/document'

Answer 2

To get that messy controller code into the model I've done this:
def process_media
temp = "#{::Rails.root}/public/temporary/#{temp_file_name}"
tempfile = Magick::Image.read(self.component.image_newsletter.path).first
overlay = Magick::Image.read(self.user.logo.path).first.resize_to_fit(tempfile.columns)
rec = Magick::Draw.new
rec.stroke = "##{self.user.colour1}"
rec.fill = "##{self.user.colour1}"
rec.rectangle 0, 0, tempfile.columns, 5
lank = tempfile.extent(tempfile.columns, tempfile.rows+overlay.rows, 0 ,0)
final = lank.composite(overlay, Magick::SouthGravity, 0, 0, Magick::OverCompositeOp)
rec.draw(final)
final.to_blob
final.write("#{temp}.jpg")
end
And I'm sending the actual file with send_file from the controller. Hope that helps someone.