Heroku rails deployement issues - ruby-on-rails

Question

currently i try to upload my rails app to heroku, but i am having this issues on my CLI:
2013-03-16T14:21:28+00:00 app[web.1]: Processing by PostsController#index as HTML
2013-03-16T14:21:28+00:00 app[web.1]: Completed 500 Internal Server Error in 1ms
2013-03-16T14:21:28+00:00 app[web.1]:
2013-03-16T14:21:28+00:00 app[web.1]: NoMethodError (undefined method `accept' for nil:NilClass):
2013-03-16T14:21:28+00:00 app[web.1]: app/controllers/posts_controller.rb:5:in `index'
2013-03-16T14:21:28+00:00 app[web.1]:
2013-03-16T14:21:28+00:00 app[web.1]:
I am not very sure about what's going on here, this is my code for routes.rb and PostsController
routes.rb
Apps2::Application.routes.draw do
devise_for :users, :controllers => { :omniauth_callbacks => "omniauth_callbacks" }
resources :posts
root :to => 'posts#index'
end
PostController
class PostsController < ApplicationController
# GET /posts
# GET /posts.json
def index
#posts = Post.all
respond_to do |format|
format.html # index.html.erb
format.json { render json: #posts }
end
end
# GET /posts/1
# GET /posts/1.json
def show
#post = Post.find(params[:id])
respond_to do |format|
format.html # show.html.erb
format.json { render json: #post }
end
end
# GET /posts/new
# GET /posts/new.json
def new
#post = Post.new
respond_to do |format|
format.html # new.html.erb
format.json { render json: #post }
end
end
# GET /posts/1/edit
def edit
#post = Post.find(params[:id])
end
# POST /posts
# POST /posts.json
def create
#post = Post.new(params[:post])
respond_to do |format|
if #post.save
format.html { redirect_to #post, notice: 'Post was successfully created.' }
format.json { render json: #post, status: :created, location: #post }
else
format.html { render action: "new" }
format.json { render json: #post.errors, status: :unprocessable_entity }
end
end
end
# PUT /posts/1
# PUT /posts/1.json
def update
#post = Post.find(params[:id])
respond_to do |format|
if #post.update_attributes(params[:post])
format.html { redirect_to #post, notice: 'Post was successfully updated.' }
format.json { head :no_content }
else
format.html { render action: "edit" }
format.json { render json: #post.errors, status: :unprocessable_entity }
end
end
end
# DELETE /posts/1
# DELETE /posts/1.json
def destroy
#post = Post.find(params[:id])
#post.destroy
respond_to do |format|
format.html { redirect_to posts_url }
format.json { head :no_content }
end
end
end
Thanks.

Answer 1

The problem seems to be related to your database gem. Heroku uses PostgreSQL (pg) as it's database engine, not sqlite. Make sure you're using pg in production.
See: Undefined method 'accept' for nil:NilClass after upgrading to Rails 3
In my Gemfile I do:
group :development, :test do
gem 'sqlite3'
end
group :production do
gem 'pg'
end