Upload file to save

I am new to rails and am stuck on the above.
I have used a mixture of code from the agile web dev with rails book
and what I have found with google.
I realise there are easier ways to do this with various plugins but I
would be interested to know why my code does not work.
The code runs and a file is created in the expected place but this
file is zero length so something is wrong.
Model code
class Photo < ActiveRecord::Base

belongs_to :user

validates_format_of :content_type,
:with => /^image/,
:message => “— you can only upload pictures”

def uploaded_picture=(picture_field)
self.photofile = base_part_of
self.content_type = picture_field.content_type.chomp
self.is_visible = 0
@data = picture_field.read
etc etc

Controller code
def create
@photo = Photo.new(params[:photo])
filename = @photo.photofile
directory = “public/images”
# create the file path
user= User.find(session[:userid])
path = File.join(directory, user.user_id)
if File.exist?(path) == false
path = File.join(directory, user.user_id, filename)
# write the file

File.new(path, “wb”) { |f| f.write(params[:picture_field].read) }

 File.new(path, "wb") { |f| f.write(@data) }

and the view
<% form_for(:photo,
:url => {:action => ‘create’},
:html => { :multipart => true }) do |f| %>

<%= f.text_field :caption %>

Upload your picture: <%= f.file_field("uploaded_picture") %>

<%= f.submit "Upload Photo" %>

<% end %>

So there are obviously some basics here that I have not yet “got”.

Many thanks for looking

it seems you’re trying to write @data into that file. you didn’t
initialize that variable in your controller. the only occurrence is
inside your model. but model and controller don’t share variables
(even if they have a similar name).

in such a case it is always helpful to debug your code. set a debugger
and see which variables contain which values.

also: don’t try to call methods (in your model) from your view. in
general i’d advice to stick to MVC-pattern. you could put that
uploaded_picture-code into your helper or just recode it.

for your view, if in doubt use this instead of <%= f.file_field
(“uploaded_picture”) %>

in your controller (the line you commented out):
File.new(path, “wb”) { |f| f.write(params[:chosen_file].read) }

if i didn’t miss anything, this should do the trick.

well, you got a few errors here and there. for example:
path = File.join(directory, user.user_id, filename)
i guess user doesn’t have a user_id but an id, so try:
path = File.join(directory, user.id, filename)

if you post your error-message, we can try to get there step by step.
but in general it would be best if you followed some tutorials for
your first steps.

I tried this and got an error.
My stuff was based on this website -
Ruby on Rails - File Uploading.
I wanted a photo stored in images/user-id/ whereas this only uses
images/. So if I remove the user-id directory, and do this, I still
get an empty file.
Thanks for you replies - I need to think my rails usage.