01-user.rb

class User < ActiveRecord::Base

  has_secure_password

  validates :email,
    presence: true,
    uniqueness: true

end

02-schema.rb

ActiveRecord::Schema.define(:version => 20120330150918) do

  create_table "users", :force => true do |t|
    t.datetime "created_at",                              :null => false
    t.datetime "updated_at",                              :null => false
    t.string   "email"
    t.string   "password_digest"
  end

end

03-routes.rb

AppName::Application.routes.draw do

  resource :sign_in
  resource :sign_up

end

04-sign_ins_controller.rb

class SignInsController < ApplicationController

  def new
  end

  def create
    @user = User.find_by_email(params[:email])

    if @user && @user.authenticate(params[:password])
      sign_in @user
      flash[:success] = "Welcome! You have been signed in."
      redirect_to @user
    else
      flash.now[:error] = "Sorry! We were unable to sign you in."
      render "new"
    end
  end

  def destroy
    session.delete(:user_id)
    redirect_to home_path
  end
end

05-sign_ups_controller.rb

class SignUpsController < ApplicationController

  def new
    @user = User.new
  end

  def create
    @user = User.new(params[:user])    

    if @user.save
      flash[:success] = "Welcome!"
      sign_in @user
      redirect_to @user
    else
      flash.now[:error] = "Sorry! We were unable to sign you up."
      render "new"
    end
  end

end