Create two hashes from one form - ruby-on-rails

Question

I want every user to upload a profile image on sign up. I have two models, a User model, and an Image model. So how should I update the User model with a new user, and an Image model with a new image for that user with one form?
user model
class User < ActiveRecord::Base
has_one :profile_image, class_name: 'Image', foreign_key: 'user_id'
end
image model
class Image < ActiveRecord::Base
# do I need to put something else here to make this relationship work?
end
user/new view
<%= form_for(#user) do |f| %>
<%= f.label :email %><br>
<%= f.text_field :email %>
<%= f.label :password %><br>
<%= f.password_field :password %>
# this needs to update a seperate params hash, but how?
<%= f.file_field :profile_image %>
<%= f.label :password_confirmation %><br>
<%= f.password_field :password_confirmation %>
<div class="actions">
<%= f.submit %>
</div>
<% end %>
user#create action
def create
#user = User.new(user_params)
respond_to do |format|
if #user.save
# save their uploaded image
Image.create() # help needed here!
sign_in #user
format.html { redirect_to #user, notice: 'Welcome, ' + #user.user_name + '!' }
format.json { render action: 'show', status: :created, location: #user }
else
format.html { render action: 'new' }
format.json { render json: #user.errors, status: :unprocessable_entity }
end
end
end
private
# how do I create a method to require certain parameters for the Image?
def user_params
params.require(:user).permit(:email, :password, :password_confirmation, :profile_image)
end
Now I've actually done the hard bit of creating their image in the filesystem (via rmagick), the easy bit, simply updating the images table with information pertaining to this image, is where I'm struggling!
Also I know of nested forms, but I'm thinking the new image and the new user should both be created in the users#create action. It makes it a lot easier to see what's going on rather than if the image was created in its own image#create action. I was also thinking of putting the user creation and the image creation in a transaction block, but this is impossible if they were both happening in their own actions, so I do think the answer is splitting a form into two params hashes and doing something with the first hash, then doing something else with the second hash.

Answer 1

Use accepts_nested_attributes_for, it's a little hard to figure out at first, but it's exactly what you need in this case. Something like this:
user.rb:
class User < ActiveRecord::Base
has_one :profile_image, class_name: 'Image', foreign_key: 'user_id'
accepts_nested_attributes_for :profile_image
end
the view:
<%= f.fields_for :profile_image do |f| %>
<%= file_field :file %>
<% end %>
The controller seems to be all set.