Edit/Update nested models (update_attributes error) - ruby-on-rails

Question

I am getting the following error when submitting an update form with nested models in Rails 3.2. Any help with this will be greatly appreciated.
NoMethodError in ProfilesController#update
undefined method `update_attributes' for nil:NilClass
Rails.root: C:/Documents and Settings/Workspace/project_x
Application Trace | Framework Trace | Full Trace
app/controllers/profiles_controller.rb:32:in `update'
Request
Parameters:
{"utf8"=>"✓",
"_method"=>"put",
"authenticity_token"=>"PQFLzhgvFzRyJ2BT/GdIpjRiOM729JoYQUHrZGUi08c=",
"profile"=>{"addresses_attributes"=>{"0"=>{"address1"=>"588 brodie",
"address2"=>"Apt1115",
"city"=>"Austin",
"state"=>"Alabama",
"zip"=>"78745",
"id"=>"1"}},
"vital_attributes"=>{"birthday(2i)"=>"1",
"birthday(3i)"=>"11",
"birthday(1i)"=>"1910",
"height_feet"=>"3",
"height_inches"=>"3",
"weight"=>"220",
"id"=>"1"},
"certificate_attributes"=>{"C_ASEL"=>"1",
"C_AMEL"=>"1",
"C_ASES"=>"1",
"C_AMES"=>"0",
"ATP_ASEL"=>"0",
"ATP_AMEL"=>"0",
"ATP_ASES"=>"0",
"ATP_AMES"=>"0",
"FI_ASE"=>"1",
"FI_AME"=>"1",
"FI_INSTA"=>"1",
"GI_Basic"=>"0",
"GI_Advanced"=>"0",
"GI_Instrument"=>"0",
"id"=>"1"}},
"commit"=>"Save & Continue",
"id"=>"1"}
Here are the models, controller, and form involved:
class Profile < ActiveRecord::Base
attr_accessible :addresses_attributes, :vital_attributes, :certificate_attributes
belongs_to :contact
has_many :addresses
has_one :certificate
has_one :vital
accepts_nested_attributes_for :addresses, :certificate, :vital
end
class Address < ActiveRecord::Base
belongs_to :profile
end
class Vital < ActiveRecord::Base
belongs_to :profile
end
class Certificate < ActiveRecord::Base
belongs_to :profile
end
class ProfilesController < ApplicationController
before_filter :authenticate, :only => [:show, :edit, :update]
before_filter :correct_contact, :only => [:show, :edit, :update]
.
.
.
def edit
#profile = Profile.find(params[:id])
#address = #profile.addresses.first
#vital = #profile.vital
#certificate = #profile.certificate
end
def update
if #profile.update_attributes(params[:profile])
flash[:success] = "Profile updated"
render 'edit'
else
render 'edit'
end
end
private #######################################################################
def authenticate
deny_access unless signed_in?
end
def correct_contact
#contact = Contact.find(params[:id])
redirect_to(root_path) unless current_contact?(#contact)
end
end
<%= form_for #profile, :html => { :class => "form-horizontal" } do |f| %>
<%= f.fields_for :addresses do |aa| %>
<%= aa.label :address1, "Address 1:", :class => "control-label" %>
<%=aa.label :address2, "Address 2:", :class => "control-label" %>
<%=aa.text_field :address2 %>
<%= aa.label :city, "City:", :class => "control-label" %>
<%= aa.text_field :city %>
<%= aa.label :state, "State:", :class => "control-label" %>
<%= aa.select(:state, options_for_select([["Alabama", "Alabama"], ["Texas", "Texas"]]), {}, :class => "select-auto-size") %>
<%= aa.label :zip, "Zip Code:", :class => "control-label" %>
<%= aa.text_field :zip %>
<% end %>
<%= f.fields_for :vital do |ab| %>
<%= ab.label :birthday, "Birthday:", :class => "control-label" %>
<%= ab.date_select :birthday, { :start_year => 1910, :end_year => 1995, :order => [:month, :day, :year] },{ :class => "select-auto-size" } %>
<%= ab.label :sex, "Sex:", :class => "control-label" %>
<%= ab.radio_button :sex, "Male", :id => "optionRadios1" %> Male
<%= ab.radio_button :sex, "Female", :id => "optionRadios2" %> Female
<%= ab.label :height, "Height:", :class => "control-label" %>
<%= ab.select(:height_feet, options_for_select([["3'", 3], ["4'", 4]]), {}, :class => "select-auto-size") %>
<%= ab.select(:height_inches, options_for_select([["3''", 3], ["4''", 4]]), {}, :class => "select-auto-size") %>
<%= ab.label :weight, "Weight:", :class => "control-label" %>
<%= ab.text_field :weight, :class => "input-mini" %><span>
<% end %>
<%= f.fields_for :certificate do |ac| %>
<label class="checkbox"><%= ac.check_box :C_ASEL %> Single</label>
<label class="checkbox"><%= ac.check_box :C_AMEL %> Multi</label>
<label class="checkbox"><%= ac.check_box :C_ASES %> Other</label>
<% end %>
<%= f.submit "Save & Continue", :class => "btn" %>
<% end %>

Answer 1

undefined method `update_attributes' for nil:NilClass
This is telling you that in your update controller action in ProfilesController you are calling update_attributes on a variable that is currently nil instead of an instance of the model you're trying to update. Specifically
def update
if #profile.update_attributes(params[:profile])
# ...
You are not assigning #profile to any model instance, so it's nil. You must do what you've done in your edit action.
def update
#profile = Profile.find(params[:id])
if #profile.update_attributes(params[:profile])
# ...