days_controller.rb

class DaysController < ApplicationController
  #before_filter :get_day, :only => [:show, :edit, :update, :destroy]
  
  def get_day
    @day = Day.find(params[:id])
  end
  
  def index
    @days = Day.all
  end
  
  def show
    @day = Day.find(params[:id])
    @habit = @day.habit
  end

  def new
    @day = Day.new
  end

  def create
    @day = Day.new(params[:day])
    if @day.save
      redirect_to days_path
    else
      render "new"
    end
  end
  
  def edit
    @day = Day.find(params[:id])
  end
  
  def update
    @day = Day.find(params[:id])
    if @day.update_attributes(params[:day])
      redirect_to days_path
    else
      render "edit"
    end
  end
  
  def destroy
    @day = Day.find(params[:id])
    @day.destroy
    redirect_to days_path
  end
end

habits_controller.rb

class HabitsController < ApplicationController

  def index
  end

  def show
  end
  
  def new
    @day = Day.find(params[:day_id])
    @habit = @day.build_habit
  end
  
  def create
    @day = Day.find(params[:day_id])
    @habit = @day.build_habit(params[:habit])
    if @habit.save!
      redirect_to @day
    else
      render "new"
    end
  end

  def edit
  end


end

habits_form.html.erb

<%= form_for([@day, @habit]) do |h| %>
  <%= h.label :energy %><br>
  <%= h.text_field :energy %><br>

  <%= h.label :mood %><br>
  <%= h.text_field :mood %><br>

  <%= h.label :overall %><br>
  <%= h.text_area :overall, :size => "34x21" %><br><br>

  <%= h.submit "Create" %>
<% end %>

models

class Day < ActiveRecord::Base
  attr_accessible :sleep, :wake
  has_one :habit
end


class Habit < ActiveRecord::Base
  belongs_to :day
  attr_accessible :energy, :mood, :overall
end

Routes

Life::Application.routes.draw do

  root :to => "Days#index"
  
  resources :days do 
    resources :habits
  end
  
end

stack-trace

NoMethodError in Days#show

Showing /Users/tomlyons/Desktop/rails_projects/life/app/views/days/show.html.erb where line #38 raised:

undefined method `energy' for nil:NilClass
Extracted source (around line #38):

35:  
36:   <tbody>
37: 	<tr>
38: 	  <td><%= @habit.energy  %></td>
39: 	  <td><%= @habit.mood  %></td>
40: 	  <td><%= @habit.overall  %></td>
41: 	</tr>
Rails.root: /Users/tomlyons/Desktop/rails_projects/life