Rails Routes.rb - ruby-on-rails

Question

How does rails know how to map to each function in the controller if the routes.rb file only specifies:
resources :users
but inside the UsersController you have
class UsersController < ApplicationController
# GET /users
# GET /users.json
def index
#users = User.all
respond_to do |format|
format.html # index.html.erb
format.json { render :json => #users }
end
end
# GET /users/1
# GET /users/1.json
def show
#user = User.find(params[:id])
respond_to do |format|
format.html # show.html.erb
format.json { render :json => #user }
end
end
# GET /users/new
# GET /users/new.json
def new
#user = User.new
respond_to do |format|
format.html # new.html.erb
format.json { render :json => #user }
end
end
# GET /users/1/edit
def edit
#user = User.find(params[:id])
end
# POST /users
# POST /users.json
def create
#user = User.new(params[:user])
respond_to do |format|
if #user.save
format.html { redirect_to #user, :notice => 'User was successfully created.' }
format.json { render :json => #user, :status => :created, :location => #user }
else
format.html { render :action => "new" }
format.json { render :json => #user.errors, :status => :unprocessable_entity }
end
end
end
# PUT /users/1
# PUT /users/1.json
def update
#user = User.find(params[:id])
respond_to do |format|
if #user.update_attributes(params[:user])
format.html { redirect_to #user, :notice => 'User was successfully updated.' }
format.json { head :no_content }
else
format.html { render :action => "edit" }
format.json { render :json => #user.errors, :status => :unprocessable_entity }
end
end
end
# DELETE /users/1
# DELETE /users/1.json
def destroy
#user = User.find(params[:id])
#user.destroy
respond_to do |format|
format.html { redirect_to users_url }
format.json { head :no_content }
end
end
end
How does rails determine that for instance the index function maps to GET/users while the create function maps to POST/users?
How does resources :users even know to map to the UsersController?

Answer 1

Rails is based around the 'convention over configuration' paradigm.
As such, the "resources :users" line indicates that all the standard CRUD methods are supported by the corresponding UsersController <-- the 'Users' prefix matches to the Controller, Model etc.

Answer 2

Please check the rails routes guide: http://guides.rubyonrails.org/routing.html
And to see in practice what the routes declaration does issue this command in your project directory:
rake routes
Also as mentioned before, stick with conventions and remember that rails is a very opinionated piece of software.