40+ Frequently Asked Ruby on Rails Interview Questions and Answers [2023]

Ruby on Rails is probably the most famous Ruby framework. Its popularity is due to its ease of use, MVC architecture, community, and scalability.

Major companies using Ruby on Rails include GitHub, Dribble, Shopify, Airbnb, Etsy, Kickstarter, Twitch, and Zendesk, to name a few.

If you’re an intermediate or seasoned Ruby on Rails engineer, it’s a smart move to understand the nature of the questions you’re likely to find in your next interview.

Interviews can be scary if you’re not prepared. However, if you are well prepared, your confidence will skyrocket and you may be lucky enough to land a new role at your dream company.

These are common Ruby on Rails interview questions and answers.

What is Ruby on Rails?

Ruby is an object-oriented programming language with a simple syntax.

Ruby on Rails is a Ruby framework that developers use to create web applications.

Discuss the benefits of Ruby on Rails

• Less code than other languages : With Rails, you can accomplish a lot with just a few lines of code.
• Extensive library and gems : There are a large number of libraries and gems available to improve the functionality of your Ruby on Rails apps.
• Easy to learn: Ruby on Rails code looks like plain English.
• It’s a big community.

Discuss the limitations of Ruby on Rails

• Compared to Django and Node.js, Rails’ execution speed and performance are low.
• Limited documentation on some gemstones.
• Ruby on Rails is arbitrary, which limits developer flexibility.

What is a Rails controller?

This is the logical heart of a Ruby on Rails application. Rails controllers manage, orchestrate, and monitor all interactions between users, models, and views.

What is active record in Rails?

Active Record is an object-relation mapping (ORM) technology. This layer of Ruby code runs between your code logic and the database. After writing your Ruby code, run a “migration” to make changes to your database.

What is MVC and how does it work?

The Model View Controller (MVC) architectural pattern separates business logic from input and presentation logic.

• Model: Handles all the data logic within your Rails app.
• View : This is the part of the application that the user sees.
• Controller : It’s like a bridge or broker that allows models and views to communicate.

What is an action controller in Ruby on Rails?

The action controller is C in the MVC pattern. Action controllers receive incoming requests, understand them, and produce the appropriate output.

What is rake in Rails?

Rake is a task runner for Ruby on Rails and Ruby applications. Rails has predefined Rake tasks for running tests, running migrations, and creating databases.

What is yield in Ruby on Rails?

Yield is a keyword used within the method that calls the block. There is no limit to the number of arguments that Yield can pass to a block. A block in this case is an unnamed method that can be passed as additional arguments to other methods.

What is garbage collection Ruby on Rails?

Garbage collection is the process of controlling memory used by computer programs. Ruby on Rails tracks which objects are used by the program, not by the programmer. Therefore, developers can focus on logic and rules instead of worrying about memory allocation.

What is the role of garbage collection in Rails apps?

This frees up memory on your machine for other processes to run. Garbage collection accomplishes this by removing inaccessible objects left behind by a program after execution.

What is an asset pipeline?

The Ruby on Rails asset pipeline provides a framework for minifying and concatenating CSS and JavaScript assets. This framework allows you to automatically combine all assets in your Rails app with assets from other gems.

Distinguish between dynamic and static scaffolding

Scaffolding is the process of generating the main parts of a Rails application.

Static scaffolding involves explicitly entering commands to generate the required data for each field. To complete static scaffolding, you must perform a migration.

Dynamic scaffolding generates content and user interfaces at runtime. This process can be used to create, modify, and delete actions in your Rails app.

What is a class library?

Class libraries consist of domains in Ruby on Rails, and thread programming and data types are examples of such domains. Class libraries allow developers to create code abstractions so they can use the same logic within different elements within an app.

Explaining polymorphic associations in Rails

A polymorphic association is a type of active record association. Polymorphism means that an object can have many forms. In the context of Rails, polymorphic associations allow you to define a single model that can be related to and belong to other models without writing repeated code.

What is string interpolation in Ruby?

String interpolation adds placeholders that refer to other values ​​within a string object. Using the addition operator is the simplest way to interpolate values.

Consider the following example.

 name = "Titus"

puts "Hello " + name

The output should look like this:

Hello, Titus

What is an object-relationship model (ORM)?

ORM is a bridge between databases and object-oriented programs. Object relationships in Rails indicate when classes are mapped to tables in the database.

Explaining Rails migration

Migration allows developers to easily change database schemas. Therefore, developers can manage database schema rollouts and rollbacks in a controlled environment. This method eliminates the ability to manage individual SQL scripts to define changes.

Explaining Rails naming conventions

• Classes and modules: Use MixedCase, but no underscores. Class and module names start with an uppercase letter.
• Database tables: Database table names must be plural and snakecase.
• Variables : The letters that declare variables must be lowercase, snakecase, and separated by underscores.
• Model : Specify the model using MixedCase and ensure the name is singular.
• Controllers: Controller names are plural.

What is the difference between string and text in Rails?

:string is suitable for storing short texts of up to 255 characters. Can be used with name, username, email, password, and title.

:text is suitable for long descriptions. A perfect example of a comment on a blog post or store description.

 class CreatePosts < ActiveRecord::Migration

   def self.up

      create_table:posts do |t|

         t.string:description

         t.text :content 

      end

   end

Describe Cross-Site Request Forgery (CSRF)

Cross-site request forgery (CSRF) is an online attack in which an attacker traps an authenticated user into performing specific actions on that user’s behalf.

Rails requires developers to add “protect_from_forgery” to ApplicationController to avoid CSRF attacks. Apps always require a CSRF token to authenticate users.

Explaining what a Rails mixin is

Mixins provide a controlled way to add functionality to your classes. Various mixins make up a class. Mixins eliminate the need to have multiple inheritance.

How to use load and require in Ruby?

require( ) is used to import libraries/gems

load() is used to execute a block of code

What is the difference between callbacks and observers in Ruby on Rails

Rails observers are used when a method is not directly related to the object’s lifecycle. It has a large life cycle and can be installed or removed at any time.

Callbacks can only be called on specific instances within an object’s lifecycle. Examples of such instances include update, create, and validate. Callbacks are only active for a short period of time.

What is Ruby’s harness and equipment?

Fixtures refer to the way you organize the data you are testing. These can be created in files that end with a .yml extension.

Harnesses are environments or test runners for running Rails tests. Place the equipment on the harness.

What is the difference between extendand include?

” Include” adds instance methods to a class. Therefore, the code will be accessible via class methods.

” Extend” adds instance methods defined in the module to the extended class.

Are gems and plugins the same in Ruby?

Gems are packaged Ruby applications that you need to install. They are generic and functionally independent of Rails.

Ruby on Rails plugins are deployed together with your Rails application. These modify or add to the core functionality of Rails.

What is a Railway Observer?

Rails observers provide a mechanism for one object to notify other objects when its state changes. This can be applied to one-to-many relationships, such as when one object changes, all dependent objects are notified and changed automatically.

What commands are used to create migrations?

 bin/rails db:migrate 

Shows how to define classes, instances, and global variables in Ruby.

• Class variables: Can be used anywhere within a class. Descendants of the class can also access them. Starts with @@.
• Instance variables: Used in a local scope specific to the instance of the created object. They may differ from object to object. Starts with @.
• Global variables: Can be accessed from anywhere in the program. Starts with $.

What role does the rakefile in the Ruby demo directory play?

Rakefiles are useful for testing and packaging your Rails code. This file defines tasks that run tests or demonstrate the functionality of your application.

What is a sweeper in Rails?

Sweepers act as terminators on caches. They act as half filters and half observers and implement dual role callbacks. ‘expire_cache’ finds and clears all cache fragments that need to be expired.

What is a filter?

These are the “before” or “after” methods in which the controller’s actions are performed. Such methods are inherited and run on every request your app receives, as long as they are configured in the ApplicationController.

Distinguishing between redirection and rendering in Rails

Render: Used to render the template and send it to the client upon request. This template generates a page that is displayed in a browser.

Redirect : Send a new HTTP request to a different URL. This action redirects the client to another controller or action. This method is useful if you want to change the URL that clients display in their browsers.

Distinguishing between calls to super() and super calls

• Super : Sends a message to the parent of the current object and calls all arguments of the called method.
• super(): No arguments are sent to the parent.

What is the difference between a procedure and a block?

• Block: A A do/end statement or a piece of code enclosed in curly braces. These are created and executed every time the method is called.
• Procs: A block of code bound to a set of local variables. This code can be called in different contexts and still access the variables.

What is the difference between put and print statements?

If you want to print something on the screen, use put . for example,

 puts “Hello World!!!”

Print Hello World. on screen

If you don’t want to add new lines to the console, use print.

 print “Hello World!!!” 

Hello World!!! is printed, but no new line is added to the console.

What is a dynamic viewfinder?

Dynamic finders allow developers to search for records in a database without using raw SQL queries. These use the find_by_ keyword followed by the attribute to search for.

Explaining how Rail implements Ajax

• Triggers such as form submissions and button clicks are initiated.
• The JavaScript method sends the trigger data to the server’s handler.
• The server-side handler processes the data and sends the HTML to the web client.
• A client-side JavaScript handler receives the HTML content and updates the current page.

Explain Dig, Float, and Max

• The Dig method allows you to extract values ​​from nested hashes or arrays.
• Float is a Ruby data type that represents a real number with floating point precision.
• Max is a method that can be used with arrays and hashes. Returns the maximum value of a collection of items/values.

 array = [2, 9, 4, 7, 3]

maximum = array.max

The console prints 9, the highest number.

conclusion

Above are some questions you’re likely to encounter at the next Ruby on Rails. If you are a general software engineer, check out these Node.js interview questions. Before attending your next interview, be sure to understand what a Rails engineer does.