Rails foreign key is nil in nested form - ruby-on-rails

Question

I have a couple models (Site and Server) that are related to eachother via has_many :through. they also both belong_to :user. in my sites/new view, I create a new site, and I create a new server using a nested form.fields_for :servers. Everything works as expected, except for that the server that ends up getting created doesn't have a user_id populated. How do i ensure it is?
My sites_controller new and create methods:
def new
#user = current_user
#site = #user.sites.build
#servers = #user.servers.all
# let there be one server linked
#site.site_servers.build
# #user.servers.build if #user.servers.empty?
#site.servers.build( :user_id => current_user.id ) if #site.servers.empty?
respond_to do |format|
format.html # new.html.erb
format.xml { render :xml => #site }
end
end
def create
#site = current_user.sites.build(params[:site])
respond_to do |format|
if #site.save
flash[:notice] = 'Site was successfully created.'
format.html { redirect_to(#site) }
format.xml { render :xml => #site, :status => :created, :location => #site }
else
format.html { render :action => "new" }
format.xml { render :xml => #site.errors, :status => :unprocessable_entity }
end
end
end
If you notice the commented lines, those are things I tried that didn't work.
Models:
class User < ActiveRecord::Base
acts_as_authentic
has_many :sites
has_many :servers
end
class Site < ActiveRecord::Base
belongs_to :user
has_many :site_servers
has_many :servers, :through => :site_servers
accepts_nested_attributes_for :site_servers, :allow_destroy => true
accepts_nested_attributes_for :servers, :allow_destroy => true
validates_presence_of :name, :on => :create, :message => "Name is required"
end
class Server < ActiveRecord::Base
attr_encrypted :password, :key => '393b79433f616f445f652a752d', :attribute => 'crypted_password'
belongs_to :user
has_many :site_servers
has_many :sites, :through => :site_servers
validates_presence_of :url, :on => :create, :message => "URL is required."
validates_presence_of :username, :on => :create, :message => "Username is required."
validates_presence_of :password, :on => :create, :message => "Password is required."
def name
username + "#" + url
end
def to_s
name
end
end
class SiteServer < ActiveRecord::Base
belongs_to :site
belongs_to :server
has_one :user, :through => :site
end
And here's my schema:
ActiveRecord::Schema.define(:version => 20091203045550) do
create_table "servers", :force => true do |t|
t.string "url"
t.string "username"
t.string "crypted_password"
t.integer "port"
t.integer "user_id"
t.datetime "created_at"
t.datetime "updated_at"
end
create_table "site_servers", :force => true do |t|
t.integer "site_id"
t.integer "server_id"
t.datetime "created_at"
t.datetime "updated_at"
end
create_table "sites", :force => true do |t|
t.string "name"
t.string "url"
t.string "path"
t.integer "user_id"
t.datetime "created_at"
t.datetime "updated_at"
end
create_table "users", :force => true do |t|
t.string "username"
t.string "email"
t.string "crypted_password"
t.string "password_salt"
t.string "persistence_token"
t.datetime "created_at"
t.datetime "updated_at"
end
end

Answer 1

Do you have a hidden field for the user_id in the server form?
<%= f.hidden_field :user_id %>
If not, the value is not getting passed back, even if you managed to properly set it. The line you have commented out would have worked, if you add a hidden field to the form.
#site.servers.build(:user_id => current_user.id) if #site.servers.empty?
I actually like the idea of setting the user id in the create method better, because otherwise you introduce the possibility of someone crafting up their own form submission and creating things under other people's user ids. I don't know if security is a big deal in your app, but I never trust a user id that is sent from a form.

Answer 2

I'm guessing the problem is in your create action. The new action just builds Ruby objects -- you need to make sure there is similar build code in the create action:
def create
#site = current_user.sites.build(params[:site])
#site.save
end