Rails routes, kind of synonym routes - ruby-on-rails-3

Question

Statement
Imagine we have an inventory app, there it is a Movement model, it represent any movement like products purchase or products sale. So we have default REST routes.
movements GET /movements(.:format) {:action=>"index", :controller=>"movements"}
POST /movements(.:format) {:action=>"create", :controller=>"movements"}
new_movement GET /movements/new(.:format) {:action=>"new", :controller=>"movements"}
edit_movement GET /movements/:id/edit(.:format) {:action=>"edit", :controller=>"movements"}
movement GET /movements/:id(.:format) {:action=>"show", :controller=>"movements"}
PUT /movements/:id(.:format) {:action=>"update", :controller=>"movements"}
DELETE /movements/:id(.:format) {:action=>"destroy", :controller=>"movements"}
For mnemonic proposes, we want to have some descriptive routes, like:
new_purchase /purchase/new(.:format) {:controller=>"movements", :action=>"new_purchase"}
edit_purchase /purchase/:id/edit(.:format) {:controller=>"movements", :action=>"edit_purchase"}
If you can see purchase's are same model likemovement's, actually are processed by MovementsController, but there with have different flow and treatment, this specified by create_purchase instead of create.
Questions
How should I add restful routes for purchase's? Taking care of specify HTTP methods like GET, POST, PUT, DELETE, etc.
How should I write form_for tags? Using movement model we can write: <%= form_for(#movement) do |f| %> but how is to call purchase paths for create or update methods?
How should I specify validation rules for purchase's? I have specified some rules on Movement model, but they are not applied for purchase's when a form is submitted.

Answer 1

You could use some thing like this in your routes file
match '/purchase/new(.:format)' => 'movements#new_purchase' :via => :get
match '/purchase/:id/edit(.:format)' => 'movements#edit_purchase' :via => :post
and you can mention others like delete, put in :via
for more info look at this link
If you want to change create to create_purchases go to the movements controller and change the definition names.
for the second question you could do something like this
form_tag(:controller => "controller_name", :action => "action_name", :method => "get")

Answer 2

I don't think that you should be looking for a way to RESTfully build routes for a model that handles an object in two separate ways. That sounds to me like you're really looking for two objects. You can create a Purchase model that inherits its properties from a parent Movement model.
Alternatively, you could assume that they are the same object and handle them the same way with semantic paths that make sense. That said, what you're looking for may be a path alteration for the default RESTful routes of the Movement controller actions. Also, a typical rails convention is to use plural path routes, which makes semantic sense for index pages and identifying objects that are a subset of a table of objects in a database, so I'm using purchases instead of purchase.
resources :movements, :path => "/purchases"
will produce
movements GET /purchases(.:format) {:action=>"index", :controller=>"movements"}
POST /purchases(.:format) {:action=>"create", :controller=>"movements"}
new_movement GET /purchases/new(.:format) {:action=>"new", :controller=>"movements"}
edit_movement GET /purchases/:id/edit(.:format) {:action=>"edit", :controller=>"movements"}
movement GET /purchases/:id(.:format) {:action=>"show", :controller=>"movements"}
PUT /purchases/:id(.:format) {:action=>"update", :controller=>"movements"}
DELETE /purchases/:id(.:format) {:action=>"destroy", :controller=>"movements"}
Using this model, the form_for helper method can still be used just like you would normally. Assuming #movement is properly defined, the path with the purchases root will be called properly.