First Rails application - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What does this Rails controller action render?

Consider this Rails controller code. What will the browser display when visiting the index action?

Ruby on Rails

class ArticlesController < ApplicationController
  def index
    @articles = ['Ruby', 'Rails', 'MVC']
  end
end

A A plain page showing the list: Ruby, Rails, MVC

B A JSON response with the articles array

C A blank page because no view template is provided

D An error because there is no explicit render call

💡 Hint

Rails automatically renders a view matching the action name if no render call is given.

Rails by default renders the view template matching the controller action name. Here, index will render app/views/articles/index.html.erb which can use @articles to display the list.

📝 Syntax

intermediate

Identify the syntax error in this Rails route definition

Which option correctly fixes the syntax error in this routes file snippet?

Ruby on Rails

Rails.application.routes.draw do
  get 'welcome/index'
  root to: 'welcome#index'
  resources :articles
  get 'articles/show/:id' => 'articles#show'
end

A Replace <code>root to: 'welcome#index'</code> with <code>root 'welcome#index'</code>

B Add a comma after <code>resources :articles</code>

C Change <code>get 'articles/show/:id' => 'articles#show'</code> to <code>get 'articles/:id' => 'articles#show'</code>

D Remove the <code>get 'welcome/index'</code> line

💡 Hint

Check the URL pattern for the show action in RESTful routes.

The route get 'articles/show/:id' is not a standard RESTful pattern and may cause confusion. The correct pattern is get 'articles/:id' which matches the show action properly.

❓ state_output

advanced

What is the output of this Rails view code?

Given the controller sets @name = 'Alice', what will this ERB template output?

Ruby on Rails

<h1>Welcome, <%= @name.upcase %>!</h1>
<p>Today is <%= Date.today.strftime('%A') %>.</p>

A <h1>Welcome, ALICE!</h1><p>Today is Monday.</p>

B <h1>Welcome, Alice!</h1><p>Today is Monday.</p>

C <h1>Welcome, ALICE!</h1><p>Today is <%= Date.today.strftime('%A') %>.</p>

D An error because <code>Date</code> is not available in views

💡 Hint

ERB evaluates Ruby code inside <%= %> and Date is accessible in views.

The @name.upcase converts 'Alice' to 'ALICE'. The Date.today.strftime('%A') outputs the current weekday name, e.g., 'Monday'.

🔧 Debug

advanced

Why does this Rails form not submit data?

This form in a Rails view does not send data to the controller. What is the cause?

Ruby on Rails

<%= form_with url: articles_path, method: :post do %>
  <%= text_field_tag :title %>
  <%= submit_tag 'Create' %>
<% end %>

A The form block is missing a variable for the form builder

B The form_with helper uses remote: true by default, so no page reload occurs

C The text_field_tag is not inside the form block properly

D The form_with helper requires a model object to submit data

💡 Hint

Check the default behavior of form_with regarding remote submission.

By default, form_with submits data via AJAX (remote: true), so the page does not reload. If the controller does not handle AJAX, it may seem like the form does nothing.

🧠 Conceptual

expert

What is the role of the ApplicationController in a Rails app?

Choose the best description of ApplicationController in a Rails application.

A It defines the routes and URL mappings for the application

B It handles database connections and queries for all models

C It is the main view template that all pages render by default

D It is the base controller that other controllers inherit from, sharing common behavior and filters

💡 Hint

Think about inheritance and shared code in controllers.

ApplicationController is the parent class for all controllers in Rails. It allows sharing methods, filters, and behavior across controllers.