Ruby on Rails Paperclip avatar, undefined method `model_name' for NilClass:Class

Question

I was on Railstutrial on chapter 7 where it tries to add user avatars.

I tried to use paperclip to let users upload their own avatar, instead of using default book guid on using gravatar in railstutorial, chapter 7.
So I found this tutrial and did the stuff until:
This is the DB Migration ([timestamp]_add_attachments_avatar_to_user.rb)

class AddAttachmentsAvatarToUser < ActiveRecord::Migration
  def self.up
    add_column :users, :avatar_file_name, :string
    add_column :users, :avatar_content_type, :string
    add_column :users, :avatar_file_size, :integer
    add_column :users, :avatar_updated_at, :datetime
  end

  def self.down
    remove_column :users, :avatar_updated_at
    remove_column :users, :avatar_file_name
    remove_column :users, :avatar_content_type
    remove_column :users, :avatar_file_size
  end
end

This is UsersController (users_controller.rb)

class UsersController < ApplicationController
  def show
    @user = User.find(params[:id])
  end

  def new
    @user = User.new
  end

  def create
    @user = User.new(params[:user])
    if @user.save
      flash[:success] = "Welcome to My Site"
      redirect_to @user
    else
      render 'new'
    end
  end
end  

This is User Model (user.rb)

class User < ActiveRecord::Base
  attr_accessible :name, :email, :password, :password_confirmation,
                  :avatar,
                  :avatar_file_name,
                  :avatar_content_type,
                  :avatar_file_size,
                  :avatar_updated_at
  has_secure_password
  has_attached_file :avatar, :styles => { :large => "120x120>", :medium => "48x48>", :thumb => "26x26>" }
  before_save { |user| user.email = email.downcase }
  validates :name,  presence: true, length: { maximum: 50 }
  VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i  
  validates :email, presence: true,
                    format: { with: VALID_EMAIL_REGEX },
                    uniqueness: { case_sensitive: false }
  validates :password, presence: true, length: { minimum: 6 }
  validates :password_confirmation, presence: true
end  

This is Routes file (routes.rb)

FinalProject::Application.routes.draw do
  resources :users
  root to: 'static_pages#home'
  match '/signup',  to: 'users#new'
  match '/help',    to: 'static_pages#help'
  match '/about',   to: 'static_pages#about'
  match '/terms',   to: 'static_pages#terms'
end  

This is the form in my view (new.html.erb) Updated

<% provide(:title, 'Sign up') %>
<h1>Sign up</h1>

<div class="row">
  <div class="span6 offset3">
    <%= form_for @user, :html => { :multipart => true } do |f| %>
      <%= render 'shared/error_messages' %>
  
      <%= f.label :name %>
      <%= f.text_field :name %>

      <%= f.label :email %>
      <%= f.text_field :email %>

      <%= f.label :password %>
      <%= f.password_field :password %>

      <%= f.label :password_confirmation, "Confirmation" %>
      <%= f.password_field :password_confirmation %>
  
      <%= f.label 'avatar' %>
      <%= f.file_field :avatar %>

      <%= f.submit "Create my account", class: "btn btn-large btn-primary" %>
    <% end %>
  </div>
</div> 

and finally this is the error, when I try to signup a new user:

NoMethodError in Users#new

Showing /home/[username]/rails_projects/final_project/app/views/users/new.html.erb where line #6 raised:

undefined method `model_name' for NilClass:Class

Please Help!

---

UPDATED

This is the form helper the auther proposed on reinventar.com:

<% form_for :user, @user, :url => user_path, :html => { :multipart => true } do |f| %>

Where as I decided to use this:

<%= form_for @user, :html => { :multipart => true } do |f| %>  

I Think this should be the source of conflict!

---

UPDATED

As I added th :url => user_path to the form_for helper, now It is giving me the following error:

Routing Error
No route matches {:action=>"show", :controller=>"users"}

I think It can not go to user page after posting form data to server!

Answer 1

It should be users_path, not user_path

EDIT

users_path        =>  /users     # This URL gets routed to users#create for a
                                 # POST method and users#index for a GET method

user_path(@user)  =>  /users/55  # This URL gets routed to users#show for a GET
                                 # method and users#destroy for a DELETE method