Rails3: Rendering from another controller

I am getting started with rails, so this is a fairly basic question. I am trying to render a login form (authlogic) in the homepage, using this code:

views/home/index.html.haml:

%p
  This is the home page...!

- if current_user
- else
  = render :template => 'user_sessions/new'

user_sessions_controller:

class UserSessionsController < ApplicationController
  before_filter :require_no_user, :only => [:new, :create]
  before_filter :require_user, :only => :destroy

  def new
    @user_session = UserSession.new
  end

  def create
    @user_session = UserSession.new(params[:user_session])
    if @user_session.save
      flash[:notice] = "Login successful!"
      redirect_back_or_default user_controls_url
    else
      render :action => :new
    end
  end

  def destroy
    current_user_session.destroy
    flash[:notice] = "Logout successful!"
    redirect_back_or_default home_url
  end
end

views/user_sessions/new.html.haml

= form_for @user_session, :url => {:action => "create"} do |f|
  = f.error_messages
  %div
    = f.label :login
    = f.text_field :login
  %div
    = f.label :password
    = f.password_field :password
  %div
    = f.check_box :remember_me
    = f.label :remember_me
  %div
    = f.submit "Login"

models/user_session.rb

class UserSession < Authlogic::Session::Base

  def to_key
    new_record? ? nil : [ self.send(self.class.primary_key) ]
  end

  httponly true
  secure true
end

When I visit the homepage, I get:

ActionView::Tem开发者_JAVA技巧plate::Error (undefined method `model_name' for NilClass:Class):
1: = form_for @user_session, :url => {:action => "create"} do |f|
2:   = f.error_messages
3:   %div
4:     = f.label :login
  app/views/user_sessions/new.html.haml:1:in `_app_views_user_sessions_new_html_haml___182031841_97682750'
  app/views/home/index.html.haml:6:in `_app_views_home_index_html_haml__679857083_97787190'

What am I doing wrong, and how do I fix it?

Thanks a lot for your help.

---

In your code, @user_session is being created when you visit the new action that is connected to user_sessions/new; it is not created when you go to the index action.

When you render the user_sessions/new template from the index action, ERB/HAML is looking for an instance of @user_session and cannot find it, hence the error.

So, you could instantiate @user_session like this:

#Note: The <%%> is ERB code (please adjust it for the syntax used in HAML)
<% @user_session = UserSession.new if @user_session.nil? %>

= form_for @user_session, :url => {:action => "create"} do |f|
...

Or, you can also do it in the index action itself, though it would be better to keep it out from the index action and instead do it as above (eg. what if you want to render the template from some other action as well - then you would be duplicating code unnecessarily)