How to upload an image to S3 using paperclip gem - ruby-on-rails

Question

For the life of my I can't understand how the basic paperclip example works. There's only one line included in the controller, and that's
#user = User.create( params[:user] )
I simply don't understand how that's all that is needed to upload an image to s3. I've changed the example quite a bit because i wanted to use jquery file uploader rather than the default rails form helper, so I'm at the point where an image is being POSTed to my controller, but I can't figure out how I'm supposed to take the image from the params and assign it as an attachment. Here's what I'm seeing the logs:
Parameters: {"files"=>[#<ActionDispatch::Http::UploadedFile:0x132263b98 #tempfile=#<File:/var/folders/5d/6r3qnvmx0754lr5t13_y1vd80000gn/T/RackMultipart20120329-71039-1b1ewde-0>, #headers="Content-Disposition: form-data; name=\"files[]\"; filename=\"background.png\"\r\nContent-Type: image/png\r\n", #content_type="image/png", #original_filename="background.png">], "id"=>"385"}
My JS is very simple:
` $('#fileupload').fileupload({
dataType: 'json',
url: '/my_url',
done: function (e, data) {
console.log('done');
}
});`
What would be helpful for me to know is how I can strip the file data from the POSTed parameters given above and pass it to paperclip. I'm sure that I'll have to assign the attachment attribute a value of File.open(...), but I dont know what source of my file is.
I've spent a ridiculous amount of time trying to figure this out and I can't seem to get it. I've tried uploading directly to s3, but the chain of events was terribly confusing, so I want to get this simple pass-through example completed first. Thanks so much for any help you cna give!

Answer 1

You need a few more pieces and it will help if you can show the exact code you're using.
Paperclip can post to S3 by using:
http://rubydoc.info/gems/paperclip/Paperclip/Storage/S3
When your controller creates a User model, it is sending along all the params. This is called "mass assignment" (be sure to read about attr_accessible).
When your model receives the params, it uses the Paperclip AWS processor, which uploads it.
You need the AWS gem, a valid bucket on S3, and a config file.
Try this blog post and let us know if it helps you:
http://blog.trydionel.com/2009/11/08/using-paperclip-with-amazon-s3/
UPDATE 2013-04-03: Pleases see Chloe's comment below-- you may need an additional parameter, and the blog post may be outdated.

Answer 2

If you want to do it manually, approach it like this:
# In order to get contents of the POST request with the photo,
# you need to read contents of request
upload = params[:file].is_a(String)
file_name = upload ? params[:file] : params[:file].original_filename
extension = file_name.split('.').last
# We have to create a temp file which is going to be used by Paperclip for
# its upload
tmp_file = "#{Rails.root}/tmp/file.#{extension}"
file_id = 0
# Check if file with the name exists and generate unique path
while File.exists?(tmp_file) do
tmp_file_path = "#{Rails.root}/tmp/file#{file_id}.#{extension}"
id += 1
end
# Let's write the file from post request to unique location
File.open(tmp_file_path, 'wb') do |f|
if upload
f.write request.body.read
else
f.write params[:file].read
end
end
# Now that file is saved in temp location, we can use Paperclip to mimic one file
# upload
#photo = Photo.new :photo => File.open(tmp_file_path)
# We'll return javascript to say that the file is uploaded and put its thumbnail in
# HTML or whatever else you wanted to do with it
respond_to do |format|
if #photo.save
render :text => "Success"
else
render :text => #photo.errors
end
end
You can rewrite your create or whatever you use as the url to which you are POSTing the form.

Answer 3

This bit:
"files"=>[#<ActionDispatch::Http::UploadedFile:0x132263b98 #tempfile=# <File:/var/folders/5d/6r3qnvmx0754lr5t13_y1vd80000gn/T/RackMultipart20120329-71039-1b1ewde-0>
is the part (I think) that holds the file contents that are posted in the form.
In Rails, the User model will have a helper: has_attached_file
Passing the [:params] to the User.create method allows that helper to pick up the file contents, do any processing on them (eg resizing etc based on attributes supplied to the helper) and then push the image(s) to your storage (eg S3 or whatever - S3 credentials are passed to the helper).
Hopefully that explains the 'how does it do it?' question
re the jQuery bit.. not sure what the code should be there, but why not use the Rails form with :remote => true and handle the response in jquery?