Route definition in routes.rb in Ruby on Rails - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the routes.rb file in a Rails application?

The routes.rb file defines how URLs map to controller actions. It tells Rails what code to run when a user visits a specific web address.

beginner

How do you define a simple route that maps the URL /home to the index action of the home controller?

You write:
get '/home', to: 'home#index'
This means when someone visits /home, Rails runs the index method in the home controller.

intermediate

What does the resources :posts line do in routes.rb?

It creates all the standard routes for a resource named posts. This includes routes for showing, creating, editing, updating, and deleting posts automatically.

beginner

Explain the difference between get and post in route definitions.

get defines a route for retrieving data (like showing a page). post defines a route for sending data to the server (like submitting a form).

beginner

How can you set the root URL (homepage) of your Rails app in routes.rb?

Use the root method like this:
root 'welcome#index'
This means the homepage URL / runs the index action of the welcome controller.

What does this route do? get '/about', to: 'pages#about'

A Maps the URL /about to the about action in pages controller

B Creates a new page called about

C Deletes the about page

D Redirects /about to the home page

The route connects the URL /about to the about method inside the pages controller.

Which HTTP method is used to submit form data in Rails routes?

A post

B get

C put

D delete

post is used to send data to the server, like submitting forms.

What does resources :users generate?

A Only the show route for users

B A single route for creating users

C All standard RESTful routes for users

D No routes, just a placeholder

It creates all common routes like index, show, new, edit, create, update, and destroy for users.

How do you set the homepage route in Rails?

A start 'welcome#index'

B home 'welcome#index'

C get '/', to: 'welcome#index'

D root 'welcome#index'

The root method sets the homepage route.

Which file do you edit to define routes in a Rails app?

A application.rb

B routes.rb

C config.yml

D database.rb

Routes are defined in the config/routes.rb file.

Describe how you would create a route for a 'contact' page that shows a form using the 'pages' controller and 'contact' action.

Think about how to connect a URL to a controller action using get.

Explain what the resources method does in Rails routing and why it is useful.

It saves time by generating many routes for common actions.

Practice

1. What is the purpose of defining routes in the routes.rb file in a Rails application?

easy

A. To manage user sessions

B. To write database queries

C. To style the web pages

D. To connect URLs to specific controller actions

Solution

1. Step 1: Understand the role of routes in Rails

   Routes define how incoming web requests are matched to controller actions.

2. Step 2: Identify the correct purpose

   Connecting URLs to controller actions allows the app to respond correctly to user requests.

3. Final Answer:

   To connect URLs to specific controller actions -> Option D

4. Quick Check:

   Routes link URLs to actions [OK]

Hint: Routes map URLs to controller actions [OK]

Common Mistakes:

• Confusing routes with database queries
• Thinking routes handle styling
• Assuming routes manage sessions

2. Which of the following is the correct syntax to define a GET route for the URL /home that maps to the index action of the pages controller?

easy

A. route get '/home' => 'pages#index'

B. get 'pages#index', to: '/home'

C. get '/home', to: 'pages#index'

D. post '/home', to: 'pages#index'

Solution

1. Step 1: Recall the syntax for GET routes in Rails

   The correct syntax is get 'url', to: 'controller#action'.

2. Step 2: Match the URL and controller#action correctly

   get '/home', to: 'pages#index' correctly uses get '/home', to: 'pages#index'.

3. Final Answer:

   get '/home', to: 'pages#index' -> Option C

4. Quick Check:

   GET route syntax = get 'url', to: 'controller#action' [OK]

Hint: Use get 'url', to: 'controller#action' for GET routes [OK]

Common Mistakes:

• Swapping URL and controller#action positions
• Using post instead of get for GET routes
• Incorrect syntax like 'route get'

3. Given the following route definition in routes.rb:

resources :articles, only: [:index, :show]

What URLs will be available and which controller actions will they map to?

medium

A. /articles (GET) -> articles#index and /articles/:id (GET) -> articles#show

B. /articles/new (GET) -> articles#new and /articles/:id/edit (GET) -> articles#edit

C. /articles (POST) -> articles#create and /articles/:id (PATCH) -> articles#update

D. /articles/:id (DELETE) -> articles#destroy and /articles (GET) -> articles#index

Solution

1. Step 1: Understand the resources with only option

   It limits routes to only index and show actions.

2. Step 2: Identify URLs and actions for index and show

   index maps to GET /articles, show maps to GET /articles/:id.

3. Final Answer:

   /articles (GET) -> articles#index and /articles/:id (GET) -> articles#show -> Option A

4. Quick Check:

   resources with only index, show = GET /articles and GET /articles/:id [OK]

Hint: Only index and show create GET /collection and GET /collection/:id [OK]

Common Mistakes:

• Assuming all RESTful routes are created
• Confusing HTTP verbs for actions
• Mixing up new/edit with index/show

4. Identify the error in this route definition:

get '/profile', controller: 'users', action: 'show'

medium

A. URL should not start with a slash

B. Missing 'to:' keyword before controller#action

C. Should use 'post' instead of 'get'

D. Controller name should be capitalized

Solution

1. Step 1: Check correct syntax for get route with controller and action

   The correct syntax uses to: 'controller#action', not separate keys.

2. Step 2: Identify the missing 'to:' keyword

   The given code misses to: and incorrectly uses separate keys.

3. Final Answer:

   Missing 'to:' keyword before controller#action -> Option B

4. Quick Check:

   Use get '/url', to: 'controller#action' [OK]

Hint: Use 'to:' keyword for controller#action in routes [OK]

Common Mistakes:

• Omitting 'to:' keyword
• Using wrong HTTP verb
• Incorrect URL format

5. You want to create routes for a blog with posts and nested comments. Which route definition correctly creates RESTful routes for posts and nested comments inside routes.rb?

hard

A. resources :posts do
resources :comments
end

B. resources :posts, comments: true

C. resource :posts do
resource :comments
end

D. get '/posts/:post_id/comments', to: 'comments#index' only

Solution

1. Step 1: Understand nested resources syntax

   Nested resources are defined by placing one resources block inside another.

2. Step 2: Identify correct nested syntax for posts and comments

   resources :posts do resources :comments end correctly nests comments inside posts using a block.

3. Final Answer:

   resources :posts do resources :comments end -> Option A

4. Quick Check:

   Nested resources use block syntax [OK]

Hint: Nest resources inside block for nested routes [OK]

Common Mistakes:

• Using singular 'resource' instead of plural 'resources'
• Trying to pass nested resources as options
• Defining only one route manually