undefined method in rails - ruby-on-rails

Question

I get the error
undefined method `favorite_relationships_path'
when I display this form:
<%= form_for(current_user.favorite_relationships.build(lesson_id: #lesson.id),
remote: true) do |f| %>
<div><%= f.hidden_field :lesson_id %></div>
<%= f.submit "Favorite", class: "btn btn-large btn-primary" %>
<% end %>
I'm not sure why. I have a controller called favorite_relationships_controller.rb and a model file, favorite_relationship.rb, with the code
class FavoriteRelationship < ActiveRecord::Base
attr_accessible :lesson_id
belongs_to :user
belongs_to :lesson
end
My user model also has:
has_many :favorite_relationships
has_many :lessons, :through => :favorite_relationships
I'm really not sure why im getting that error. Help would be appreciated.

Answer 1

Rails has _path and _url helpers for routes, which are set up in config/routes.rb. You'll need to ensure that you've defined the routes for FavouriteRelationshipController; something like:
resources :favourite_relationships
You can check the routes defined for your application using the rake routes command.
You can find more information about routing at the Rails Routing from the Outside In guide.

Answer 2

Defining controllers, actions and views is not enough. You need to define routes in config/routes.rb to connect URLs to your controllers/actions. Defining RESTful resources with resources :favourite_relationships in your routing file is what causes Rails to generate the *_path and *_url helpers; until you do this there is no way for requests to reach your app, and no way for your app to generate routes based on your models.
Your routes file should look something like this:
MyApp::Application.routes.draw do
resources :favourite_relationships
end
This generates the typical "CRUD" routes required for a RESTful resource:
favourite_relationships GET /favourite_relationships(.:format) {:action=>"index", :controller=>"favourite_relationships"}
POST /favourite_relationships(.:format) {:action=>"create", :controller=>"favourite_relationships"}
new_favourite_relationship GET /favourite_relationships/new(.:format) {:action=>"new", :controller=>"favourite_relationships"}
edit_favourite_relationship GET /favourite_relationships/:id/edit(.:format) {:action=>"edit", :controller=>"favourite_relationships"}
favourite_relationship GET /favourite_relationships/:id(.:format) {:action=>"show", :controller=>"favourite_relationships"}
PUT /favourite_relationships/:id(.:format) {:action=>"update", :controller=>"favourite_relationships"}
DELETE /favourite_relationships/:id(.:format) {:action=>"destroy", :controller=>"favourite_relationships"}