Rails 3 undefined method nil:NilClass has_many :through when attempting create

Question

I am encountering a problem when trying to .build a new appointment. But first a look at my Model(s)

class Patient < ActiveRecord::Base
  attr_accessible :address1, :address2, :city, :comment, :email, :first_name, :init_date,    :init_time, :last_name, :mobile, :notes, :phone, :state, :zip
  before_validation :upcase_patient
  before_save { self.email.downcase! }
  has_many :appointments, dependent: :destroy
  has_many :procedures, through: :appointments

class Procedure < ActiveRecord::Base
  attr_accessible :comment, :occurence, :procedure, :procedure_code, :procedure_price, :procedure_time, :visits
  before_validation :uppercase_procedure
  has_many :appointments
  has_many :patients, through: :appointments

class Appointment < ActiveRecord::Base
  attr_accessible :appointment_date, :appointment_notes, :appointment_time, :procedure_id
  belongs_to :patient
  belongs_to :procedure

class AppointmentsController < ApplicationController
include PatientsHelper
before_filter :signed_in_user

def create
    @patient = current_patient
    @appointment = @patient.appointments.build(params[:appointment])
    if @appointment.save
        flash[:success] = "Appointment scheduled!"
        redirect_to patient_path(@patient)
    else
        render patient_path(@patient)
    end
end

module PatientsHelper

    def current_patient=(patient)
            @current_patient = patient
    end

    def current_patient
            @current_patient
    end

    def current_patient?(patient)
            patient == current_patient
    end
end

These items including "PatientsHelper" which helps define current_patient make up the associations. I have created the form successfullly within the patients_controller

class PatientsController < ApplicationController
before_filter :signed_in_user
before_filter :admin_user, only: [:destroy]
def show
    @patient = Patient.find(params[:id])
    @procedures = Procedure.all
    @appointments = @patient.appointments.paginate(page: params[:page])
    @appointment = @patient.appointments.build
end

I would like to use the patients resources to create new appointments. Here is where I am fouled up. I continue to receive via rspec the following error:

NoMethodError:
   undefined method `appointments' for nil:NilClass

Where am I going wrong? Any help would be greatly appreciated. If clarification is required, I would like to:

a_ associate

Patient model -> has_many [:appointments, :procedures (through :appointments)]

Procedure model -> has_many [:appointments, :patients (through :appointments)]

Appointment model -> belongs_to [:patients, :procedures]

b_ create new :appointments through the patients controller rather than create a new controller specifically for appointments model

my mistake! here is the spec test.

require 'spec_helper'

describe "Appointment Pages" do
    subject { page }

    let(:user) { FactoryGirl.create(:user) }
    let(:patient) { FactoryGirl.create(:patient) }
    let(:procedure) { FactoryGirl.create(:procedure) } 
    before { sign_in user }

    describe "appointment creation" do
  before { visit patient_path(patient) }

  describe "with invalid information" do

    it "should not create an appointment" do
        expect { click_button "Schedule procedure" }.not_to change(Appointment,
                                                                                                                             :count)
    end

    describe "error messages" do
        before { click_button "Schedule procedure" }
        it { should have_content('error') }
    end
end

describe "with valid information" do
    before do
      procedure_id = procedure.id
      patient_id = patient.id
      fill_in 'appointment_appointment_date', with: "2013-04-04"
      fill_in 'appointment_appointment_time', with: "12:45:00"
      fill_in 'appointment_appointment_notes', with: "Test the notes"
    end
    it "should create a micropost" do
        expect { click_button "Schedule procedure" }.to change(Appointment, 
                                                                                                                    :count).by(1)
      end
    end
  end
end

errors show up on the following

Failures:

1) Appointment Pages appointment creation with invalid information should not create an appointment
 Failure/Error: expect { click_button "Schedule procedure" }.not_to change(Appointment,
 NoMethodError:
   undefined method `appointments' for nil:NilClass
 # ./app/controllers/appointments_controller.rb:7:in `create'
 # (eval):2:in `click_button'
 # ./spec/requests/appointment_pages_spec.rb:17:in `block (5 levels) in <top (required)>'
 # ./spec/requests/appointment_pages_spec.rb:17:in `block (4 levels) in <top (required)>'

2) Appointment Pages appointment creation with invalid information error messages 
 Failure/Error: before { click_button "Schedule procedure" }
 NoMethodError:
   undefined method `appointments' for nil:NilClass
 # ./app/controllers/appointments_controller.rb:7:in `create'
 # (eval):2:in `click_button'
 # ./spec/requests/appointment_pages_spec.rb:22:in `block (5 levels) in <top (required)>'

3) Appointment Pages appointment creation with valid information should create a micropost
 Failure/Error: expect { click_button "Schedule procedure" }.to change(Appointment,
 NoMethodError:
   undefined method `appointments' for nil:NilClass
 # ./app/controllers/appointments_controller.rb:7:in `create'
 # (eval):2:in `click_button'
 # ./spec/requests/appointment_pages_spec.rb:36:in `block (5 levels) in <top (required)>'
 # ./spec/requests/appointment_pages_spec.rb:36:in `block (4 levels) in <top (required)>'

Finished in 1.08 seconds
23 examples, 3 failures

Failed examples:

rspec ./spec/requests/appointment_pages_spec.rb:16 # Appointment Pages appointment creation with invalid information should not create an appointment
rspec ./spec/requests/appointment_pages_spec.rb:23 # Appointment Pages appointment creation with invalid information error messages 
rspec ./spec/requests/appointment_pages_spec.rb:35 # Appointment Pages appointment creation with valid information should create a micropost

Answer 1

Not exactly what I was looking for but made this work-around.

Using the following was able to get this to save accordingly. Still cannot find out why I am unable to pull the Patient from the URL -- example would be app.dev/patients/2 -- where patient information is pulling id 2... but now I am able to save the Appointment using what I suspect is a rather crude method.

1. In the form I added a hidden field which pulls the appropriate patient_id
2. In Appointments controller, added to attr_accessible :patient_id

3. In appointments_controller

   def create
   @appointment = Appointment.new(params[:appointment])
   @current_patient = @appointment.patient_id
   if @appointment.save
       flash[:success] = "Appointment scheduled!"
       redirect_to patient_path(@current_patient)
   else
       render 'patients/show'
   end
   end
   

render 'patients/show' remains broken but will leave that for another thread. Thank you all for your help and guidance.