Rails 3 and paperclip on update method issue - ruby-on-rails

Question

Paperclip is working well to save a user avatar but I find an issue on update.
In my view, if the user has an image saved in the model it will show an image tag with the current image next to the file upload field so you can see what your current avatar is.
If the image has no changes but the model validation fails (like no first_name), the original display image disappears, meaning that the user either has to correct the error and re-select an image and submit (update) or go back and start over without the error. Any ideas? Thanks in advance.
Heres the code:
Model
class User < ActiveRecord::Base
# Validation
validates :first_name, :presence => true
# Paperclip
has_attached_file :avatar, :styles => { :medium => "300x300>", :thumb => "70x70#" }
end
Controller
...
# GET /users/1/edit
def edit
#user = User.find(params[:id])
end
# POST /users
# POST /users.xml
def create
#user = User.new(params[:user])
respond_to do |format|
if #user.save
format.html { redirect_to(#user, :notice => 'User was successfully created.') }
format.xml { render :xml => #user, :status => :created, :location => #user }
else
format.html { render :action => "new" }
format.xml { render :xml => #user.errors, :status => :unprocessable_entity }
end
end
end
# PUT /users/1
# PUT /users/1.xml
def update
#user = User.find(params[:id])
respond_to do |format|
if #user.update_attributes(params[:user])
format.html { redirect_to(#user, :notice => 'User was successfully updated.') }
format.xml { head :ok }
else
format.html { render :action => "edit" }
format.xml { render :xml => #user.errors, :status => :unprocessable_entity }
end
end
end
...
View
<%= form_for #user, :html => {:multipart => true} do |f| %>
<div class="row text">
<%= f.label :first_name %>
<div class="field">
<%= f.text_field :first_name %>
</div>
</div>
<div class="row">
<%= f.label :avatar %>
<div class="field">
<%= image_tag #user.avatar.url(:thumb) %>
</div>
<div class="field" id="avatar_upload">
<%= f.file_field :avatar %>
</div>
</div>
<div class="row actions"><%= f.submit %> or <%= link_to 'cancel', users_path %>.</div>
<% end %>

Answer 1

This is being caused by your form sending 'nil' to the server (due to the field being blank since a new avatar is not being uploaded) when your page sends a POST request to your server. Short of mucking things up with hidden temporary fields, there are a few ways around this:
Client-side validation. Prevent your page from submitting if anything is wrong and you won't end up reaching the server-side validation failure that results in the missing image.
Move the avatar field to a separate FORM object on the same page that only handles the avatar. That will ensure that the page only ever sends avatar information in a POST message if it is related to an actual avatar edit.
Move the avatar upload/update functionality to a completely separate page that only handles the avatar. This works for the same reason the reason above this one works.