index.html.erb

<h1>Listing users</h1>

<table>
  <tr>
    <th>Firstname</th>
    <th>Lastname</th>
    <th>Email</th>
    <th>Facebook ID</th>
    <th>Facebook Username</th>
    <th>Username</th>
    <th></th>
    <th></th>
    <th></th>
  </tr>

<% @users.each do |user| %>
  <tr>
    <td><%= user.try(:firstname) %></td>
    <td><%= user.try(:lastname) %></td>
    <td><%= user.try(:email) %></td>
    <td><%= user.try(:facebook_id) %></td>
    <td><%= user.try(:facebook_username) %></td>
    <td><%= user.try(:username) %></td>
    <td><%= link_to 'Show', user %></td>
    <td><%= link_to 'Edit', edit_user_path(user) %></td>
    <td><%= link_to 'Destroy', user, method: :delete, data: { confirm: 'Are you sure?' } %></td>
  </tr>
<% end %>
</table>

<br />

<%= link_to 'New User', new_user_path %>

rake routes

          users GET    /users(.:format)                       users#index
                POST   /users(.:format)                       users#create
       new_user GET    /users/new(.:format)                   users#new
      edit_user GET    /users/:id/edit(.:format)              users#edit
           user GET    /users/:id(.:format)                   users#show
                PUT    /users/:id(.:format)                   users#update
                DELETE /users/:id(.:format)                   users#destroy

server response users

Started GET "/users" for 71.205.143.222 at 2013-03-04 03:54:09 +0000
2013-03-04T03:54:09+00:00 app[web.1]: Processing by UsersController#index as HTML
2013-03-04T03:54:09+00:00 app[web.1]:   Rendered users/index.html.erb within layouts/application (6.5ms)
2013-03-04T03:54:09+00:00 app[web.1]: Completed 500 Internal Server Error in 20ms
2013-03-04T03:54:09+00:00 app[web.1]: ActionController::RoutingError (No route matches {:action=>"show", :controller=>"users", :id=>#<User id: 15, firstname: "Jennifer", lastname: "Chaiwitz", email: nil, username: nil, created_at: "2013-03-03 01:15:45", updated_at: "2013-03-03 01:15:45", facebook_username: nil, photo_url: nil, facebook_id: 100005394060476>}):

User.rb

class User < ActiveRecord::Base


  attr_accessible :email, :facebook_id, :firstname, :lastname, :username, :facebook_username, :photo_url
  
  def to_param
    username
  end

  def as_json(options={})
    {:id                 => self.id,
     :email 	           => self.email,
     :facebook_id        => self.try(:facebook_id),
     :firstname          => self.firstname,
     :lastname  	 => self.lastname,
     :username            => self.username,
     :facebook_username   => self.try(:facebook_username),
     :photo_url	          => self.try(:photo_url)
        }
  end


end

UsersController.rb

class UsersController < ApplicationController
  # GET /users
  # GET /users.json
  def index
    @users = User.all

    respond_to do |format|
      format.html # index.html.erb
      format.json { render json: @users }
    end
  end