Alternative to render :update


#1

Hi guys and gals.

I don’t know how to explain this too well, so I’ll try my best and post
some obviously dysfunctional code (just so you can get the idea of what
I’m after if my explanation doesn’t do it.)

What I want to do is create an upload form that users can upload more
than one item with. The catch is I want to use ajax to pull off an
insert_html and update the page showing thumbnail to each file as it’s
added, while the other files are being uploaded. So, let’s say I upload
3 files, when the first one finishes it’s inserted to an unordered list
(via ajax, without reloading the page while the other two files are
still uploading), then the next file, then the last file and it ends.
I’ve been doing it fine with a single file, but now that I’ve added
multiple file uploads that controller style won’t work.

Doing something like this, which I figured was a 1,000,000:1 shot at it
working (of course, it didn’t) gives a DoubleRender error which I
expected:

def create
@project = Project.find(params[:id])

params[:attachment].each do |key, value|
if value and value != ‘’
@file = Image.new(Hash[‘uploaded_data’ => value])
@file.user_id = logged_in_user.id
@file.project_id = @project.id

  respond_to do |format|
    if @file.save
      format.js do
              responds_to_parent do
                render :update do |page|
            page.insert_html :top, "images", :partial => 'image',

:object => @file
end
end
end
else
# etc…
end
end
end
else
# etc.
end

Can this sort of thing even be pulled off?


#2

You want to execute multiple inserts in a single response, not
multiple responses. This might work, assuming that the rest of your
code works and that you are using attachments as the relationship
name.

def create
@project = Project.find(params[:id])

params[:attachment].each do |key, value|
if value and !value.blank?
new_file = Image.new(Hash[‘uploaded_data’ => value])
new_file.user_id = logged_in_user.id
@project.attachments << new_file
end
end

respond_to do |format|
if @project.save
format.js do
render :update do |page|
@project.attachments.each do |file|
page.insert_html :top, “images”, :partial =>
‘image’, :object => file
end
end
end
end
end
end

On Apr 7, 9:45 am, Jack B. removed_email_address@domain.invalid


#3

Hi Jaryl, thanks.

That would work, but it has a slightly different behavior than what I’m
looking for. I want it to begin the upload of the multiple images, let’s
say 3, and when one finishes being processed (resized, etc.) it’s
inserted into the page and then the second image starts being processed
and inserted, then the third. Your solution would process all three and
after it finishes processing it’ll dump all 3 of them out at essentially
the same time.

It’s a relatively unimportant difference, but I was wondering if there’s
a way to pull that off.


#4

Google for a Rails version of swfupload… in the Rails code it updates
the thumbnails as it processes the files.


#5

If that’s the case, then you should split it up into multiple
requests. I believe that you can only send back one response per
request, so that is an inherent problem.

Perhaps you may try sending a request once the a valid file is
selected in the file upload field.

On Apr 7, 10:04 pm, Jack B. removed_email_address@domain.invalid


#6

Jaryl Sim wrote:

If that’s the case, then you should split it up into multiple
requests. I believe that you can only send back one response per
request, so that is an inherent problem.

Sure that’s the case, that’s how HTTP protocol works. One response for
one request. I think of it as similar to an event loop, where each cycle
through the loop processes one event.

The difference is that an event loop is continuous, where a
request-response cycle sleeps between each cycle. In other words the
event loop runs continuously checking an event queue, where as HTTP
sleeps until it is sent a request, which causes it to “awake” and
process the request and generate a response. After the response is
processes it sleeps again until awoken by another request.

Perhaps you may try sending a request once the a valid file is
selected in the file upload field.

As far as I know, the behavior you’re after is going to require some
client-side code. I know there are a number of solutions floating
around, some taking advantage of Flash (as I assume the swfupload does).
Some others I’ve heard of make use of a Java applet. But, I would
imagine this behavior could be built with JavaScript/AJAX.

In any case I think the “brains” of this feature will need to be
implemented client-side. The AJAX should be able to send requests to a
server-side action responsible to accepting one file, and the
client-side code would make one request per file, plus additional
request to manipulate the DOM.

Please note this is all speculation. I have no proof-of-concept code to
offer.


#7

Thanks everyone for the replies.

For now I’m just going with good 'ol standard HTML response until I
figure out what I’m going to do.