Rails POST, PUT, GET

Question

After I generate a scaffold, Rails gives me the ability to POST to items.xml which will create a new item. A GET to items.xml will simply list them all. Where does Rails specify which method in the controller (create or index, respectively) will be called, based on the type of action I am performing?

More specifically, POST calls methodA but GET to the same URL calls methodB. Where is this specified? Where does Rails make the determination to call the index method of the controller?

Answer 1

Rails defines seven controller methods for RESTful resources by convention. They are:

Action   HTTP Method  Purpose
-------------------------------------------------------------------------
index    GET          Displays a collection of resources
show     GET          Displays a single resource
new      GET          Displays a form for creating a new resource
create   POST         Creates a new resource (new submits to this)
edit     GET          Displays a form for editing an existing resource
update   PUT          Updates an existing resource (edit submits to this)
destroy  DELETE       Destroys a single resource

Note that because web browsers generally only support GET and POST, Rails uses a hidden field to turn these into PUT and DELETE requests as appropriate.

Specifying map.resources :items in config/routes.rb gets you those seven methods "for free". You can list all the routes within your application at any time by entering rake routes in the console.

• See Rails Routing from the Outside In for more detail.

Answer 2

map.resources is a method that automagically gives you the REST routes and path helpers as well. This is a nice feature if you already know and understand how rails' restful routing works but it is also a bit of a hindrance for learning rails because too much is hidden.

Railsguides has a nice routes guide.