Ready to prove your mettle with rails interview questions? Welcome to our Ruby on Rails quiz, where you'll tackle curated ruby and rails interview questions covering everything from routing to Rails MVC questions. Perfect for backend developers hungry to sharpen their Rails framework interview questions prowess, this interactive test delivers instant feedback and insights to elevate your skills. Whether you're eyeing your next dev role or refining your knowledge, dive in now and challenge yourself! Craving more variety? Try our Django quiz for a cross-framework comparison, and supplement your preparation with dedicated interview questions practice . Unleash your inner RoR expert - start now and boost your backend game!
Which command generates a new Rails application?
rails start myapp
rails new myapp
rails generate app myapp
rails init myapp
The rails new command sets up a new Rails application skeleton including directories for models, views, and controllers. It also generates default configuration files, tests, and a Gemfile for managing dependencies. This is the standard way to bootstrap a Rails project. See the Rails getting started guide for more details: Rails Getting Started.
What is ActiveRecord in Ruby on Rails?
A templating engine
A background job processor
An ORM framework that maps models to database tables
A CSS framework
ActiveRecord is the default Object-Relational Mapping (ORM) layer in Rails, which abstracts database interactions into Ruby objects. It allows you to define models that map to database tables, making CRUD operations more intuitive. ActiveRecord handles SQL under the hood and supports relationships, validations, and callbacks. Learn more in the official guide: Active Record Basics.
Which file defines RESTful routes in a Rails application?
app/controllers/application_controller.rb
config/routes.rb
app/models/route.rb
config/application.rb
The config/routes.rb file is where Rails defines how URLs map to controller actions following RESTful conventions. You use DSL methods like resources, get, post, and root to configure routes. This file is loaded during application boot and determines the available endpoints. For more details see: Rails Routing.
Which command starts the Rails server?
rails start
rails boot
rails run server
rails server
The rails server (or rails s) command launches the default Puma server for your Rails application. By default it runs on port 3000 and listens for incoming HTTP requests. You can pass flags like -p to change the port or -b to bind to a different IP. Refer to the command documentation: Rails Server.
How do you generate a new model called 'Post' with a title:string field?
rails generate model Post title:string
rails create model Post title:string
rails new model Post title:string
rails model Post create title:string
rails generate model Post title:string creates a model class, a migration file for the database table, and test stubs. It defines a title column of type string in the migration. After running rails db:migrate, the posts table is available. See the Rails generators guide: Rails Generate.
What is a migration in Rails?
A way to version control database schema changes
A template renderer
A tool for asset compression
A background job scheduler
Migrations are Ruby classes that define database schema changes in a version-controlled manner. Each migration file can add, modify, or remove tables and columns. They ensure that your database schema remains consistent across different environments. More information is available at Active Record Migrations.
By default, which database does Rails use in the development environment?
MongoDB
SQLite
PostgreSQL
MySQL
Rails applications default to using SQLite3 in development because it requires no external setup and stores data in a file. This makes initial development and testing quick and straightforward. You can configure other databases by modifying database.yml. Refer to the database configuration guide: Configuring a Database.
Which file contains environment-specific configuration in a Rails app?
config/database.yml
config/initializers/assets.rb
config/environments/development.rb
config/application.rb
The config/environments/development.rb file holds settings that apply only to the development environment. This includes configurations like caching, error reporting, and asset debugging. Each environment (test, production) has its own file under config/environments. You can learn more at Rails Environment Configuration.
What is the difference between 'has_many' and 'has_one' associations in Rails?
has_many sets up one-to-many, has_one sets up one-to-one relationships
has_many is for database joins, has_one is for validations
has_many creates only one record, has_one creates multiple records
has_many works with callbacks, has_one doesn't
In Rails, has_many defines a one-to-many relationship where a single record can be associated with multiple records of another model. has_one sets up a one-to-one relationship, indicating only one associated record. These associations generate methods for accessing related objects and managing foreign keys. See the Active Record Associations guide for more details: Association Basics.
What does 'validates :name, presence: true' do in a Rails model?
Checks that 'name' is unique
Ensures the 'name' attribute is not blank before saving
Encrypts the 'name' attribute
Automatically trims whitespace from 'name'
validates :name, presence: true adds a validation to ensure that the name attribute is neither nil nor an empty string. If the validation fails, the record will not be saved, and errors will be populated. This is a common way to enforce required fields at the model layer. Learn more at Active Record Validations.
What does 'before_action :authenticate_user!' do in a Rails controller?
Skips authentication for all actions
Defines a helper method
Runs only after actions complete
Runs the authenticate_user! method before each action in the controller
before_action registers a callback to run the specified method before any controller action. With :authenticate_user!, it prevents unauthenticated users from accessing protected actions by redirecting them or showing an error. This is used frequently in authentication libraries like Devise. More information can be found here: Action Controller Overview.
How do you eager load the 'comments' association on a Post model?
Post.load_comments
Post.find_comments
Post.includes(:comments)
Post.joins(:comments)
Post.includes(:comments) tells ActiveRecord to load the comments association in the same query or in a separate query upfront. This prevents the N+1 query problem by fetching associated records ahead of time. joins only affects SQL JOIN operations and doesn't eager load by default. Learn more at Eager Loading Associations.
What is the asset pipeline in Rails?
A database replication system
A background processing queue
A testing framework
A framework to concatenate and minify JS and CSS assets
The asset pipeline is a Rails feature that combines, minifies, and serves JavaScript, CSS, and image assets. It uses Sprockets to process files, allowing you to write CoffeeScript, SCSS, and apply fingerprinting for cache busting. It improves page load times and manageability of front-end assets. See details at Asset Pipeline.
What is Turbolinks in Rails?
A JavaScript testing library
A tool for SQL performance
A library that speeds up navigation by using AJAX to load pages
A CSS preprocessor
Turbolinks makes web applications feel faster by intercepting link clicks and replacing the body and head of the page via AJAX without a full reload. It preserves persistent elements like JavaScript state and asset load. This reduces load times and improves perceived performance. More can be read at Turbolinks GitHub.
What is the difference between 'render' and 'redirect_to' in Rails controllers?
render is for JSON only, redirect_to is for HTML
render always reloads the page, redirect_to only updates data
render redirects to external sites, redirect_to renders views
render displays a template without a new request, redirect_to sends an HTTP redirect causing a new request
render renders a view template within the same request cycle, whereas redirect_to instructs the browser to perform a new request to a different action or URL. render does not change the URL in the browser, but redirect_to updates it. Use render to show a template and redirect_to after data changes to prevent duplicate submissions. More info here: Rendering and Redirecting.
What are strong parameters in Rails?
A performance optimization for queries
A method to compress assets
A security feature that filters allowed parameters for mass assignment
A way to encrypt parameters in URLs
Strong parameters require controllers to explicitly list which parameters are permitted for mass assignment when creating or updating models. This prevents unwanted attributes from being passed through forms. It was introduced in Rails 4 to enhance security. Read the official guide at Strong Parameters.
What is Active Job in Rails?
A module for user authentication
A view rendering helper
A framework for declaring and executing background jobs
A caching system
Active Job is a unified interface for queuing and running background jobs in Rails. It supports multiple backend queuing libraries such as Sidekiq, Resque, and Delayed Job. You write jobs in a single syntax and choose or swap adapters as needed. More information is available at Active Job Basics.
What is a polymorphic association in Rails?
A feature for API versioning
A one-to-one association
A many-to-many association
An association where a model can belong to more than one other model using a single interface
Polymorphic associations allow a model to belong to multiple other models on a single association. For example, a Picture model can belong to either a Product or a User using a polymorphic interface. This is implemented with type and id columns in the database. See the guide: Polymorphic Associations.
How do you implement Single Table Inheritance (STI) in Rails?
Use a 'type' column in the table and subclasses inherit from the base class
Use polymorphic: true in associations
Define multiple database connections
Create separate tables for each subclass
Single Table Inheritance uses a type column in a database table to distinguish between different subclasses. Subclasses inherit from a base model, and ActiveRecord uses the type field to instantiate the correct class. This allows sharing a schema across related models. Read more at ActiveRecord::Inheritance.
What is the N+1 query problem and how can you solve it in Rails?
It occurs when each record triggers a separate query; solved by eager loading associations using 'includes'
It is a security vulnerability; solved by sanitizing inputs
It happens only in production; solved by disabling logs
It is a caching issue; solved by using Redis
The N+1 query problem arises when iterating over a collection causes one additional database query per record to load an association. You can avoid this by using includes, preload, or eager_load to fetch associated records in batches. This reduces database round trips and improves performance. More details are in the querying guide: Eager Loading Associations.
What are controller concerns in Rails?
A type of background job
A database indexing feature
Modules to share reusable code between controllers
A way to validate models
Controller concerns are modules placed in app/controllers/concerns to share common behavior across multiple controllers. They help DRY up code by encapsulating shared methods, filters, or callbacks. Rails automatically includes them when you use ActiveSupport::Concern. For more info: Controller Concerns.
What is the difference between 'find' and 'find_by' methods in ActiveRecord?
'find' caches results, 'find_by' does not
'find' always returns an array, 'find_by' returns a string
'find' works only with primary keys, 'find_by' works with associations
'find' raises an exception if record not found, 'find_by' returns nil
ActiveRecord.find(id) will raise an ActiveRecord::RecordNotFound exception if no record matches the id. ActiveRecord.find_by(attribute: value) returns nil instead of raising an exception if no record is found. Use find when you expect a record to exist and want an error if it doesn't. More at Finding by Attribute.
What does the 'before_save' callback do in Rails models?
Runs after the model is saved
Only runs on validations
Encrypts sensitive attributes
Runs a method before an object is saved to the database, including on create and update
before_save is a callback invoked right before ActiveRecord writes a record to the database, whether it's being created or updated. It allows you to modify attributes or trigger other logic. Mistakes in callbacks can lead to unexpected database changes. Read more at ActiveRecord Callbacks.
How can you implement caching for a view partial in Rails?
Use 'background_job :cache' in controller
Set config.cache_views = true in environment
Wrap the partial in a transaction block
Use 'cache' helper e.g., cache(my_object) do ... end
You can cache partials by wrapping them with the cache helper, passing the object or a key to generate a fragment cache. Rails will store the rendered partial and only re-render if the object changes. This improves view performance for expensive or repeated fragments. See the caching guide: Fragment Caching.
How does Rails autoloading work with the Zeitwerk loader in development environment?
Zeitwerk handles database migrations
Zeitwerk tracks file naming conventions and directories, loading constants on first reference without requiring explicit require statements
Zeitwerk is responsible for caching view fragments
Zeitwerk compiles assets and preloads JavaScript files on startup
Zeitwerk is the code loader in modern Rails that relies on file and directory naming conventions to autoload and reload constants. In development, it watches file changes and unloads and reloads code as needed, so you rarely need explicit require statements. It ensures thread safety and efficient constant lookup. Learn more in the Rails autoloading guide: Autoloading and Reloading Constants.
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AI Study Notes
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Study Outcomes
Understand Core Rails Concepts -
Acquire a clear understanding of key Ruby on Rails concepts like MVC, ActiveRecord, and RESTful routing to confidently tackle core interview questions.
Apply MVC Architecture Knowledge -
Learn to deconstruct and explain the Model-View-Controller structure and implement it in practical Rails scenarios.
Demonstrate Best Practices in Rails Development -
Recognize and apply industry-recognized best practices such as DRY principles, security measures, and performance optimizations.
Analyze and Solve Rails Framework Challenges -
Develop problem-solving skills by tackling real-world Rails framework questions and scenarios presented in the quiz.
Evaluate Your Rails Interview Readiness -
Use instant feedback to identify your strengths and weaknesses, boost your confidence, and guide your further study.
Enhance Ruby and Rails Fluency -
Strengthen your Ruby syntax and Rails-specific knowledge to articulate clear, concise answers during interviews.
Cheat Sheet
Understanding the MVC Architecture -
The Model-View-Controller pattern underpins Rails' design, dividing your app into data (models), interfaces (views), and control flow (controllers). According to the official Ruby on Rails Guides, remembering the request-response cycle (browser → router → controller → view) is key - think "R-C-V" as your mnemonic. This concept is often tested in rails interview questions to ensure you grasp separation of concerns.
Model Associations & ActiveRecord Queries -
Rails' ActiveRecord provides intuitive methods like has_many and belongs_to to define relationships; best practices from the Rails API recommend using scopes and includes() to avoid N+1 query pitfalls. For example, use Post.includes(:comments).where(published: true) to eager-load associations. Practicing sample queries from the official guides helps solidify these Ruby on Rails quiz topics.
Routing & RESTful Conventions -
Rails enforces RESTful design via its resources shorthand: resources :articles auto-generates the seven standard CRUD routes. Memorize the CRUD mnemonic (Create-Read-Update-Delete) to map HTTP verbs (POST, GET, PATCH, DELETE) to actions. Mastering this is vital for rails framework interview questions on routing logic.
Callbacks & Lifecycle Hooks -
ActiveRecord callbacks like before_validation, after_commit, and around_save let you inject logic into the model lifecycle, but overuse can make code hard to maintain - Rails Guides suggest limiting callbacks for side effects and favoring service objects. A quick trick: group callbacks by prefix (before_, after_) to remember their firing order. Interviewers often probe your understanding of execution flow and potential pitfalls.
Strong Parameters & Security Best Practices -
To prevent mass assignment vulnerabilities, Rails 5+ requires whitelisting parameters via the permit method in controllers, as outlined by Rails security guides. Think "permit what's perfect" as a mnemonic for only allowing known keys. Interview questions on rails security often focus on identifying and fixing unpermitted attribute issues.
