## routes.rb
ActionController::Routing::Routes.draw do |map|
  map.resources :users do |p|
  	p.resources :posts
  end
  map.login "login", :controller => 'user_sessions', :action => 'new'
  map.logout "logout", :controller => 'user_sessions', :action => 'destroy'
  map.root :controller => 'pages'
  map.resources :user_sessions
  map.resources :password_resets
  map.connect ':controller/:action/:id'
  map.connect ':controller/:action/:id.:format'
end

## posts/_form.html.erb
<% form_for([:user,@post]) do |f| %>
  <%= f.error_messages %>
  <p>
    <%= f.label :title %><br />
    <%= f.text_field :title %>
  </p>
  <p>
    <%= f.label :content %><br />
    <%= f.text_area :content %>
  </p>
  <p><%= f.submit "Submit" %></p>
<% end %>

## posts_controller.rb
 [...]
  def edit
  	require_user
  	@user = current_user
    @post = Post.find(params[:id])
  end

  def update
    @post = Post.find(params[:id])
    if @post.update_attributes(params[:post])
      flash[:notice] = "Successfully updated post."
      redirect_to root_url
    else
      render :action => 'edit'
    end
  end
 [...]

## posts/show.html.erb
[...]
<% if current_user.username = @user.username %>
	<%= link_to "Edit this post", edit_user_post_url %>
<% end %>
[...]