Ruby rails: undefined method `model_name " pour NilClass:Classe

Je suis en train de faire un petit formulaire de recherche pour rechercher un utilisateur dans le ldap. Il n'a pas vraiment rien avoir à faire avec les données locales de modèle. Pas sûr pourquoi ai-je besoin de tout changement dans le contrôleur utilisateur. L'erreur est de ne pas donner la moindre idée de moi.

Modèle de la fonction de recherche dans le ldap

class User < ActiveRecord::Base
attr_accessible :user_id, :firstname, :lastname, :email, :role, :misc, :password
validates_presence_of :user_id, :firstname, :lastname, :email, :role, :on => :create
validates_uniqueness_of :user_id, :email
ROLES = ['Admin','User']
####################
SERVER = '10.10.10.1'   
PORT = 389                    
BASE = 'DC=User,DC=mysite,DC=com'   
DOMAIN = 'ldap.mysite.com'       
####################
def self.ActiveDirectoryAuthenticate(login, pass)
user = find_by_user_id(login)
if user
nil
else
return false
end
conn = Net::LDAP.new :host => SERVER,
:port => PORT,
:base => BASE,
:auth => { :username => "#{login}@#{DOMAIN}",
:password => pass,
:method => :simple }
if conn.bind
return user
else
return false
end
rescue Net::LDAP::LdapError => e
return false
end
def self.findActiveDirectory(login)
conn = Net::LDAP.new :host => SERVER,
:port => PORT,
:base => BASE,
:auth => { :username => 'admin',
:password => 'adminpass',
:method => :simple }
if  conn.bind
conn.search(:base => BASE, :filter => Net::LDAP::Filter.eq( "sAMAccountName", login ),
:attributes => ['givenName','SN','mail'], :return_result => true) do |entry|
entry.each do |attributes, values|
if "#{attributes}" == "sn"
values.each do |value|
puts "Lastname: "+"#{value}"
$lastname = "#{value}"
end
end
if "#{attributes}" == "givenname"
values.each do |value|
puts "Firstname: "+"#{value}"
$firstname = "#{value}"
end
end
if "#{attributes}" == "mail"
values.each do |value|
puts "Email: "+"#{value}"
$email = "#{value}"
end
end
end
end
return true
else
return false
end
rescue Net::LDAP::LdapError => e
return false
end
end

De l'utilisateur contrôleur -

class UsersController < ApplicationController
def new
@user = User.new
end
def create
@user = User.new(params[:user])
if @user.save
redirect_to users_added_url, :notice => "Signed up!"
else
render "new"
end
end
end

Affichage ne fonctionne PAS (app/views/users/trouver.html.erb)

<h1>Find User</h1>
<%= form_for @user do |f| %>
<% if @user.errors.any? %>
<div class="error_messages">
<h2>Form is invalid</h2>
<ul>
<% for message in @user.errors.full_messages %>
<li><%= message %></li>
<% end %>
</ul>
</div>
<% end %>
<p>
<%= f.label :Username %><br />
<%= f.text_field :username %>
</p>
<p class="button"><%= f.submit %></p>
<% end %>

Vue - est de travail (app/views/users/new.html.erb)

<h1>Add new user</h1>
<%= form_for @user do |f| %>
<% if @user.errors.any? %>
<div class="error_messages">
<h2>Form is invalid</h2>
<ul>
<% for message in @user.errors.full_messages %>
<li><%= message %></li>
<% end %>
</ul>
</div>
<% end %>
<p>
<%= f.label :Username %><br />
<%= f.text_field :user_id %>
</p>
<p>
<%= f.label :Firstname %><br />
<%= f.text_field :firstname %>
</p>
<p>
<%= f.label :Lastname %><br />
<%= f.text_field :lastname %>
</p>
<p>
<%= f.label :Email %><br />
<%= f.text_field :email %>
</p>
<p>
<%= f.label :Role %><br />
<%= f.collection_select :role, User::ROLES, :to_s, :to_s, :include_blank => false %>
</p>
<p class="button"><%= f.submit %></p>
<% end %>

routes -

# rake routes
myapp_new GET    /myapp/new(.:format)          myapp#new
root        /                            home#index
sessions_new GET    /sessions/new(.:format)      sessions#new
users_new GET    /users/new(.:format)         users#new
users_added GET    /users/added(.:format)       users#added
myapp GET    /myapp(.:format)              myapp#new
log_out GET    /log_out(.:format)           sessions#destroy
log_in GET    /log_in(.:format)            sessions#new
sign_up GET    /sign_up(.:format)           users#new
users_find GET    /users/find(.:format)        users#find
root        /                            users#new
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
sessions GET    /sessions(.:format)          sessions#index
POST   /sessions(.:format)          sessions#create
new_session GET    /sessions/new(.:format)      sessions#new
edit_session GET    /sessions/:id/edit(.:format) sessions#edit
session GET    /sessions/:id(.:format)      sessions#show
PUT    /sessions/:id(.:format)      sessions#update
DELETE /sessions/:id(.:format)      sessions#destroy

Erreur

undefined method `model_name' for NilClass:Class