RoR Routes and URL Mapping

Routes connect URLs to your application code. When a browser sends a request to your Rails app, the router reads the URL and decides which controller and action should handle it. Without routes, your app has no way to respond to any request.

Where Routes Live

All routes go in one file: config/routes.rb. Rails reads this file on every request and matches the URL to the correct destination.

How Routing Works

Browser sends: GET /articles

config/routes.rb reads every rule top to bottom
        |
        v
Finds a match: get "/articles", to: "articles#index"
        |
        v
Sends request to: ArticlesController → index action
        |
        v
Controller runs, view renders, browser gets HTML

Basic Route Syntax

A route has three parts: the HTTP verb, the URL path, and the destination.

get "/articles", to: "articles#index"
 ^        ^              ^
 verb    path         controller#action

The four HTTP verbs Rails uses:

The Root Route

The root route defines your homepage — the page users see at /.

root "articles#index"

This sends anyone visiting http://localhost:3000 to the index action in ArticlesController.

Resourceful Routes

Rails provides a shortcut that generates all seven standard routes for a resource in one line:

resources :articles

This single line creates seven routes:

Verb      URL                   Controller#Action   Purpose
--------------------------------------------------------------
GET       /articles             articles#index      List all
GET       /articles/new         articles#new        Show new form
POST      /articles             articles#create     Save new record
GET       /articles/:id         articles#show       Show one
GET       /articles/:id/edit    articles#edit       Show edit form
PATCH     /articles/:id         articles#update     Save changes
DELETE    /articles/:id         articles#destroy    Delete record

The :id in the URL is a dynamic segment. It captures whatever number appears there and makes it available in the controller as params[:id].

URL Helpers

When you use resources, Rails automatically generates helper methods for each route. These helpers produce the correct URL path so you never hardcode URLs in your views.

Route helper            Generates URL
-------------------------------------------
articles_path           /articles
new_article_path        /articles/new
article_path(@article)  /articles/3
edit_article_path(@a)   /articles/3/edit

Use them in views like this:

<a href="<%= articles_path %>">All Articles</a>
<a href="<%= new_article_path %>">Write New Article</a>
<a href="<%= article_path(@article) %>">Read This Article</a>

Named Routes

You can give any route a name using the as option:

get "/about", to: "pages#about", as: "about"
get "/contact", to: "pages#contact", as: "contact"

Now you can use about_path and contact_path in your views instead of typing the URL manually.

Route Parameters

Dynamic segments capture values from the URL:

get "/users/:id", to: "users#show"

User visits: /users/42
Controller receives: params[:id] = "42"

You can use any name for the segment:

get "/products/:category/:id", to: "products#show"

User visits: /products/electronics/7
params[:category] = "electronics"
params[:id]       = "7"

Limit Which Routes Are Generated

If your resource only needs some of the seven routes, limit them with only or except:

resources :articles, only: [:index, :show]
resources :comments, except: [:destroy]

This keeps your route table clean and prevents exposing actions that do not exist yet.

Check All Your Routes

Run this command to see every route your app currently has:

rails routes

Filter routes by name to find a specific one:

rails routes | grep article

The Routes Diagram

config/routes.rb
        |
        +-- root "pages#home"
        |
        +-- resources :articles
        |       |
        |       +-- GET  /articles        → articles#index
        |       +-- GET  /articles/new    → articles#new
        |       +-- POST /articles        → articles#create
        |       +-- GET  /articles/:id    → articles#show
        |       +-- GET  /articles/:id/edit → articles#edit
        |       +-- PATCH /articles/:id   → articles#update
        |       +-- DELETE /articles/:id  → articles#destroy
        |
        +-- get "/about", to: "pages#about", as: "about"

Redirect Routes

You can redirect one URL to another directly inside routes:

get "/home", to: redirect("/")
get "/blog", to: redirect("/articles")

When a user visits /home, Rails immediately redirects them to /. No controller needed.

Scoped Routes

Group routes under a shared path prefix using scope:

scope "/admin" do
  resources :users
  resources :posts
end

This generates URLs like /admin/users and /admin/posts while keeping the same controller names.

Routes are the entry points to your entire application. Getting comfortable with them makes everything else in Rails easier to understand and build.