Syntax Questions (relative newbie)

[lvn4weeknd]

Hey, I am working on Rails App and I am a bit wobbly on my syntax. I would like to send one of two kinds of send_file statements to a user depending on which kind of downloadable they ordered. I have basically just expanded on the depot code in the Agile Dev book.

Here is some of the code as it now stands.

  
def download
    begin
      @order = Order.find(params[:id], :conditions => "ordered_at >= DATE_SUB(NOW(), INTERVAL 1 DAY)")
    rescue
      redirect_to_index("Sorry, that's an invalid order.")
    end
    begin
      @file = @order.line_items.find(:first, :conditions => ["deliverable_id = ?", params[:file]])
    rescue
      redirect_to_index("Sorry, you did not order that file.")
      return
    end  
    send_file "#{PDF_ROOT}/#{@file.deliverable.product.title.delete " "}.pdf", :type => 'application/pdf'
  end

What I would like to change is that last send_file bit to accomodate a statement like the following:

if deliverable.type == 1
    send_file "#{PDF_ROOT}/#{@file.deliverable_id " "}.pdf", :type => 'application/pdf'

if deliverable.type == 2
    send_file "#{MP3_ROOT}/#{@file.deliverable_id " "}.mp3", :type => 'audio/mpeg'

Also, how might I structure the opposite of this next phrase:

if item.deliverable.download == 0

I mean how would I state if the deliverable does not equal 0?

Thanks a ton, in advance. Peace.

[vgarcia]

Not equal would be != like in most other programming languages

[Luke Redpath]

To answer your last question, you have two options:

if item.deliverable.download != 0

Or:

unless item.deliverable.download == 0

Whichever reads better to you.

For your main question, I would extract most of the logic to the model and I wouldn't bother storing the uploaded files in separate folders according to type because it makes things simpler and it makes little difference - the file can be stored anywhere and named anything (no file extension needed either) as long as you have a record of the content type in your database - this can be saved when its originally uploaded.

In the following example, attachments are stored in /var/www/attachments and they are saved using the format attachment_ID

The model:

class Deliverable < ActiveRecord::Base
  def self.save_path(path)
    @@save_path = path
  end

  def attachment_path
    "#{@@save_path}/attachment_#{self.id}"
  end
end

Set your attachment path, in application.rb:

Deliverable.save_path = '/var/www/attachments'

Now your controller code is as simple as:

def download
  begin
    @order = Order.find(params[:id], :conditions => "ordered_at >= DATE_SUB(NOW(), INTERVAL 1 DAY)")
  rescue
    redirect_to_index("Sorry, that's an invalid order.")
  end
  begin
    @file = @order.line_items.find(:first, :conditions => ["deliverable_id = ?", params[:file]])
  rescue
    redirect_to_index("Sorry, you did not order that file.")
    return
  end  
    send_file @file.deliverable.attachment_path, :type => @file.deliverable.content_type
end

One gotcha, even though the right content type will be sent for the download, it will simply be named attachment_ID without a file extension. Don't forget you can send a custom name for the file with send_file() so you may want to do that to give the download a more descriptive name (perhaps using some existing metadata you have about the file in the database, or perhaps the original filename if you store that in the db when its originally uploaded).

[lvn4weeknd]

Thanks, House. Like I said, I am completely novice. I would really dig any thoughts you might have on the first part of my question. Thanks again.

[lvn4weeknd]

Thanks luke, I will give it a go!

[Luke Redpath]

Here's an example taken from an app I'm working on at the moment, a knowledgebase module for part of a larger app, where knowledgebase articles can have many attachments:

class KnowledgebaseArticleAttachment < ActiveRecord::Base
	belongs_to :article,	 :foreign_key => 'knowledgebase_article_id',
						 :class_name => 'KnowledgebaseArticle'

	validates_presence_of :article, :message => 'is required'
	validates_presence_of :description 
						 
	after_save :store_file
	after_destroy :delete_file
						 
	def self.save_path=(path)
		@@save_path = path
	end
	
	def uploaded_file=(file)
		@tmp_file = file
		self.attachment_name = sanitize_filename(file.original_filename)
		self.attachment_type = file.content_type
		self.attachment_size = File.size(file)
	end
	
	def file
		File.open(self.file_path, 'r')
	end
	
	def file_path
		"#{@@save_path}/KB#{self.id}"
	end
	
	protected
		def validate_on_create
			errors.add_to_base("You must upload a file") unless @tmp_file
		end
	
	private
		def store_file
			File.open(self.file_path, "wb") do |f|
				f.write(@tmp_file.read)
			end
		end
		
		def delete_file
			File.delete(self.file_path)
		end
		
		def sanitize_filename(file_name)
			# get only the filename, not the whole path (from IE)
			just_filename = File.basename(file_name) 
			# replace all non-alphanumeric, underscore or periods with underscores
			just_filename.gsub(/[^\w\.\-]/,'_') 
		end
end

[lvn4weeknd]

Luke, thanks a lot for your help. I am running into problems with the code's structure. I am a novice and trying to get this up and running without too much restructuring of the code/database (since I am so shaky and don't want to dig a deeper hole for myself). That being said is there no way (ruthlessly efficient or not) of keeping the logic basically as is, but having those last two options there at the end of the same controller? You are right about the keeping the files in the same file paths, though, and I will definitely do it that way.

In any case, I really appreciate it. Thanks.

[Luke Redpath]

Well the absolutely simplest thing to do given the code you originally posted is:

case @file.deliverable.type
  when 1
    send_file "#{PDF_ROOT}/#{@file.deliverable_id " "}.pdf", :type => 'application/pdf'
  when 2
    send_file "#{MP3_ROOT}/#{@file.deliverable_id " "}.mp3", :type => 'audio/mpeg'
end

I'd still advise looking into refactoring things to a better solution though. As long as your code is backed up by unit tests, and with the help of migrations for your db changes, it shouldn't be too difficult.

[lvn4weeknd]

Thanks, a billion, Luke. I will give this a shot. I do think, though, that I will restructure the app in the future, but in the meantime I want to put this out into the world in a functioning state while I learn up on my Ruby knowledge. Thanks.

[lvn4weeknd]

It worked perfectly. Thanks, Luke.