R4RIN – MCQs, Mock Tests | Ruby on Rails Ruby on Rails MCQ

When rendering a partial in a view, how would you pass local variables for rendering?

1. <%= render partial: “nav”, selected: “about”}%>
2. <%= render partial: “nav”, local_variables: {selected: “about”} %>
3. <%= render partial: “nav”, locals: {selected: “about”}
4. None of the above

✅ Correct Answer: 3

Within a Rails controller, which code will prevent the parent controller’s before_action :get_feature from running?

1. skip_before_action :get_feature
2. skip :get_feature, except: []
3. prevent_action :get_feature
4. redis_cache_store

✅ Correct Answer: 1

Which statement correctly describes a difference between the form helper methods form_tag and form_for?

1. The form_tag method is for basic forms, while the form_for method is for multipart forms that include file uploads.
2. The form_tag method is for HTTP requests, while the form_for method is for AJAX requests.
3. The form_tag method typically expects a URL as its first argument, while the form_for method typically expects a model object.
4. The form_tag method is evaluated at runtime, while the form_for method is precompiled and cached.

✅ Correct Answer: 3

What is before_action (formerly known as before_filter)?

1. A trigger that is executed before an alteration of an object’s state
2. A method that is executed before an ActiveRecord model is saved
3. A callback that fires before an event is handled
4. A method in a controller that is executed before the controller action method

✅ Correct Answer: 4

Which module can you use to encapsulate a cohesive chunk of functionality into a mixin?

1. ActiveSupport::Concern
2. RailsHelper.CommonClass
3. ActiveJob::Mixin
4. ActiveSupport::Module

✅ Correct Answer: 1

In Rails, which code would you use to define a route that handles both the PUT and PATCH REST HTTP verbs?

1. put :items, include: patch
2. put ‘items’, to: ‘items#update’
3. match ‘items’, to ‘items#update’, via: [:put, :patch]
4. match :items, using: put && patch

✅ Correct Answer: 3

Which choice includes standard REST HTTP verbs?

1. GET, POST, PATCH, DELETE
2. REDIRECT, RENDER, SESSION, COOKIE
3. INDEX, SHOW, NEW, CREATE, EDIT, UPDATE, DESTROY
4. . CREATE, READ, UPDATE, DELETE

✅ Correct Answer: 1

Which ActiveRecord query prevents SQL injection?

1. Product.where(“name = #{@keyword}”)
2. Product.where(“name = ” << @keyword}
3. Product.where(“name = ?”, @keyword
4. Product.where(“name = ” + h(@keyword)

✅ Correct Answer: 3

Given this code, which statement about the database table “documents” could be expected to be true? class Document < ActiveRecord::Base belongs_to :documentable, polymorphic: true end class Product < ActiveRecord::Base has_many :documents, as: :documentable end class Service < ActiveRecord::Base has_many :documents, as: :documentable end

1. It would include a column for :type.
2. It would include columns for :documentable_id and :documentable_type.
3. It would include columns for :documentable and :type
4. It would include a column for :polymorphic_type.

✅ Correct Answer: 3

Are instance variables set within a controller method accessible within a view?

1. Yes, any instance variables that are set in an action method on a controller can be accessed and displayed in a view.
2. Yes, instance variables set within an action method are accessible within a view, but only when render is explicitly called inside the action method.
3. No, instance variables in a controller are private and are not accessible.
4. No, instance variables can never be set in a controller action method.

✅ Correct Answer: 1

When a validation of a field in a Rails model fails, where are the messages for validation errors stored?

1. my_model.errors[:field]
2. my_model.get_errors_for(:field)
3. my_model.field.error
4. my_model.all_errors.select(:field)

✅ Correct Answer: 1

How would you generate a drop-down menu that allows the user to select from a collection of product names?

1. <%= select_tag(@products) %>
2. <%= collection_select(@products) %>
3. <%= @products.each do |product| %> <% end %>
4. <%= collection_select(:product, :product_id, Product.all, :id, :name) %>

✅ Correct Answer: 4

For a Rails validator, how would you define an error message for the model attribute address with the message “This address is invalid”?

1. model.errors = This address is invalid
2. errors(model, :address) << “This address is invalid”
3. display_error_for(model, :address, “This address is invalid”)
4. model.errors[:address] << “This address is invalid”

✅ Correct Answer: 4

Given the URL helper product_path(@product), which statement would be expected to be false?

1. If sent using the PATCH HTTP method, the URL could be used to update a product in the database.
2. If sent using the POST HTTP method, the URL would create a new product in the database.
3. If sent using the GET HTTP method, the URL would execute the show action in ProductsController.
4. If sent using the DELETE HTTP method, the URL would call the destroy action by default.

✅ Correct Answer: 2

Given this code, which choice would be expected to be a true statement if the user requests the index action? class DocumentsController < ApplicationController before_action :require_login def index @documents = Document.visible.sorted end end

1. The user’s documents will be loaded.
2. The index action will run normally because :index is not listed as an argument to before_action.
3. The require_login method will automatically log in the user before running the index action.
4. The index action will not be run if the require_login method calls render or redirect_to.

✅ Correct Answer: 4

In Rails, how would you cache a partial template that is rendered?

1. render partial: ‘shared/menu’, cached: true
2. render_with_cache partial: ‘shared/menu’
3. render partial: ‘shared/menu’
4. render partial: ‘shared/menu’, cached_with_variables: {}

✅ Correct Answer: 1

What is the reason for using Concerns in Rails?

1. Concerns allow modularity and code reuse in models, controllers, and other classes.
2. Concerns are used to separate class methods from models.
3. Concerns are used to increase security of Rails applications
4. Concerns are used to refactor Rails views.

✅ Correct Answer: 1

When using an ActiveRecord model, which method will create the model instance in memory and save it to the database?

1. build
2. new
3. create
4. save

✅ Correct Answer: 3

You are using an existing database that has a table named coffee_orders. What would the ActiveRecord model be named in order to use that table?

1. CoffeeOrders
2. Coffee_Orders
3. Coffee_Orde
4. CoffeeOrder

✅ Correct Answer: 4

In ActiveRecord, what is the difference between the has_many and has_many :through associations?

1. The has_many: through association is the one-to-many equivalent to the belongs_to one-to-one association.
2. Both associations are identical, and has_many: through is maintained only for legacy purposes.
3. The has_many association is a one-to-many association, while has_many: through is a one-to-one association that matches through a third model.
4. Both are one-to-many associations but with has_many :through, the declaring model can associate through a third model.

✅ Correct Answer: 4

How do you add Ruby code inside Rails views and have its result outputted in the HTML file?

1. Create an embedded Ruby file (.html.erb) and surround the Ruby code with <% %>.
2. Insert Ruby code inside standard HTML files and surround it with <% %>. The web server will handle the rest.
3. Create an embedded Ruby file (.html.erb) and surround the Ruby code with <%= %>.
4. Put the code in an .rb file and include it in a tag of an HTML file.

✅ Correct Answer: 3

How would you render a view using a different layout in an ERB HTML view?

1. <% render ‘view_mobile’ %>
2. <% render ‘view’, use_layout: ‘mobile’ %>
3. <% render ‘view’, layout: ‘mobile’ %>
4. <% render_with_layout ‘view’, ‘mobile’ %>

✅ Correct Answer: 1

Where should you put images, JavaScript, and CSS so that they get processed by the asset pipeline?

1. app/static
2. app/images
3. app/assets
4. app/views

✅ Correct Answer: 3

In Rails, what caching stores can be used?

1. MemCacheStore, MongoDBStore, MemoryStore, and FileStore
2. MemoryStore, FileStore, and CacheCacheStore
3. MemoryStore, FileStore, MemCacheStore, RedisCacheStore, and NullStore
4. MemoryStore, FileStore, MySQLStore, and RedisCacheStore

✅ Correct Answer: 3

What is the correct way to generate a ProductsController with an index action using only the command-line tools bundled with Rails?

1. rails generate controller –options {name: “Products”, actions: “index”}
2. rails generate controller –name Products –action index
3. rails generate controller Products index
4. rails generate ProductsController –actions index

✅ Correct Answer: 3

If a model class is named Product, in which database table will ActiveRecord store and retrieve model instances?

1. product_table
2. all_products
3. products_table
4. products

✅ Correct Answer: 4

What is a popular alternative template language for generating views in a Rails app that is focused on simple abstracted markup?

1. Mustache
2. Haml
3. Liquid
4. Tilt

✅ Correct Answer: 2

When Ruby methods add an exclamation point at the end of their name (such as sort!), what does it typically indicate?

1. The method executes using “sudo” privileges.
2. Any ending line return will be omitted from the result.
3. The method will ignore exceptions that occur during execution.
4. It is a more powerful or destructive version of the method.

✅ Correct Answer: 4

What part of the code below causes the method #decrypt_data to be run? class MyModel < ApplicationRecord after_find :decrypt_data end

1. MyModel.first.update(field: ‘example’)
2. MyModel.where(id: 42)
3. MyModel.first.destroy
4. MyModel.new(field: ‘new instance’)

✅ Correct Answer: 3

Which Rails helper would you use in the application view to protect against CSRF (Cross-Site Request Forgery) attacks?

1. csrf_protection
2. csrf_helper
3. csrf_meta_tags
4. csrf

✅ Correct Answer: 3

In the model User you have the code shown below. When saving the model and model.is_admin is set to true, which callback will be called?before_save :encrypt_data, unless: ->(model) { model.is_admin }after_save :clear_cache, if: ->(model) { model.is_admin }before_destroy :notify_admin_users, if: ->(model) { model.is_admin }

1. encrypt_data
2. clear_cache
3. notify_admin_users
4. None of these callbacks will be called when is_admin is true.

✅ Correct Answer: 1

In a Rails controller, what does the code params.permit(:name, :sku) do?

1. It filters out all parameters.
2. It filters out submitted form parameters that are not named :name or :sku to make forms more secure.
3. It raises an error if parameters that are not named :name or :sku are found.
4. It raises an error if the :name and :sku parameters are set to nil.

✅ Correct Answer: 2

Review the code below. Which Ruby operator should be used to fill in the blank so that the sort method executes properly? [5,8,2,6,1,3].sort {|v1,v2| v1 _ v2}

1. =>
2. <==>
3. <=>
4. ||

✅ Correct Answer: 3

There is a bug in this code. The logout message is not appearing on the login template. What is the cause? class AccessController < ActionController::Base def destroy session[:admin_id] = nil flash[:notice] = “”You have been logged out”” render(‘login’) end

1. The string assigned to flash[:notice] will not be available until the next browser request.
2. An instance variable should be used for flash[:notice]
3. This is an invalid syntax to use to assign valuse to flash[:notice]
4. The previous value of flash[:notice] will not be cleared automatically

✅ Correct Answer: 1

Which statement about ActiveRecord models is true?

1. Each database column requres adding a matching attr_accessor declaration in the ActiveRecord model.
2. All attributes in an ActiveRecord model are read-only declared as writable using attr_accessible
3. An instance of an ActiveRecord model will have attributes that match the columns in a corresponding database table.
4. ActiveRecord models can have only attributes that have a matching database column

✅ Correct Answer: 3

Which choice best describes the expected value of @result? @result = Article.first.tags.build(name: ‘Urgent’)

1. either true or false
2. an unsaved Tag instance
3. a saved Tag instance
4. an array of Tag instances

✅ Correct Answer: 2

If a product has a user-uploadable photo, which ActiveStorage method should fill in the blank? class Product << ApplicationRecord __ :photo end

1. has_one_attached
2. has_image
3. attached_file
4. acts_as_attachment

✅ Correct Answer: 1

If the only route defined is resources :products, what is an example of a URL that could be generated by this link_to method? link_to(‘Link’, {controller: ‘products’, action: ‘index’, page: 3})

1. /products?page=3
2. /products/index/3
3. /products/page/3
4. /products/index/page/3

✅ Correct Answer: 1

Which part of the Rails framework is primarily responsible for making decisions about how to respond to a browser request?

1. view
2. controller
3. ActiveRecord
4. model

✅ Correct Answer: 2

If User is an ActiveRecord class, which choice would be expected to return an array?

1. User.where(last_name: ‘Smith’)
2. User.find_or_create(last_name: ‘Smith’)
3. User.find_by_last_name(‘Smith’)
4. User.find(‘Smith’)

✅ Correct Answer: 1

What decides which controller receives which requests?

1. model
2. view
3. web server
4. router

✅ Correct Answer: 4

When rendering a partial in a view, how would you pass local variables for rendering?

1. <%= render partial: “nav”, globals: {selected: “about”} %>
2. <%= render partial: “nav”, local_variables: {selected: “about”} %>
3. <%= render partial: “nav”, locals: {selected: “about”} %>
4. <%= render partial: “nav”, selected: “about”} %>

✅ Correct Answer: 2

Given this code, and assuming @user is an instance of User that has an assigned location, which choice would be used to return the user’s city? class Location < ActiveRecord::Base # has database columns for :city, :state has_many :users end class User < ActiveRecord::Base belovngs_to :location delegate :city, :state, to: :location, allow_nil: true, prefix: true end

1. @user.user_city
2. @user.location_city
3. @user.city
4. @user.try(:city)

✅ Correct Answer: 1

Where would this code most likely be found in a Rails project? scope :active, lambda { where(:active => true) }

1. an Active Record model
2. an ActionView template
3. an ApplicationHelper file
4. an ActionController controller

✅ Correct Answer: 1

What is a standard prerequisite for implementing Single Table Inheritance (STI)?

1. The models used for STI must mix in the module ActiveRecord::STI
2. All models used for STI must include “self.abstract_class=true”.
3. All database tables used for STI must be related to each other using a foreign key.
4. The database table used for STI must have a column named “type”.

✅ Correct Answer: 3

A way that views can share reusable code, such as formatting a date, is called a _?

1. helper
2. utility
3. controller
4. formatter

✅ Correct Answer: 1

How do you add Ruby code inside Rails views and have its result outputted in the HTML file?

1. Insert Ruby code inside standard HTML files and surround it with <% %>. The web server will handle the rest.
2. Create an embedded Ruby file (.html.erb) and surround the Ruby code with <% %>
3. Put the code in an.rb. file and include it in a tag of an HTML file.
4. Create an embedded Ruby file (.html.erb) and surround the Ruby code with <%= %>.

✅ Correct Answer: 4

You are working with a large database of portfolios that sometimes have an associated image. Which statement best explains the purpose of includes(:image) in this code? @portfolios = Portfolio.includes(:image).limit(20) @portfolios.each do |portfolio| puts portfolio.image.caption end

1. It preloads the images files using asset pipeline.
2. It selects only portfolios that have an image attached.
3. It includes the number of associated images when determining how many records to return.
4. It will execute two database queries of 21 database queries.

✅ Correct Answer: 4

After this migration has been executed, which statement would be true? class CreateGalleries < ActiveRecord::Migration def change create_table :galleries do |t| t.string :name, :bg_color t.integer :position t.boolean :visible, default: false t.timestamps end end end

1. The galleries table will have no primary key.
2. The galleries table will include a column named “updated_at”.
3. The galleries table will contain exactly seven columns.
4. The galleries table will have an index on the position column.

✅ Correct Answer: 2

Given two models, what is the issue with the query used to fetch them? class LineItem < ApplicationRecord end class Order < ApplicationRecord has_many :line_items end Order.limit(3).each { |order| puts order.line_items }

1. This query will result in extensive caching, and you will have to then deal with caching issues.
2. This query will result in the N+1 query issue. Three orders will result in four queries.
3. This query will result in the 1 query issue. Three orders will result in one query.
4. There are no issues with this query, and you are correctly limiting the number of Order models that will be loaded.

✅ Correct Answer: 2