Ruby on Rails Interview Questions

Ruby on Rails interview questions will help you ace your Ruby on Rails programmer interview. If you are interviewing for a position where you will have to work on the web application framework, Ruby on Rails, you must prepare for the most anticipated questions.

Ruby is widely used by several top companies such as Twitter, Airbnb, Hulu, Netflix, GitHub, Bloomberg, and many more. Ninety percent of Ruby web applications are written using Rails. You must prepare vital concepts such as class hierarchies, encapsulation, inheritance, and polymorphism, as well as advanced topics such as multithreading and deploying your Rails app.  

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Throughout this article, we'll look at interview questions and answers you can expect to be asked during a programmer interview at Ruby on Rails. We’ll cover:

• Basic Ruby on Rails interview questions with answers
• Ruby on Rails interview questions and answers for an experienced Ruby programmer
• Ruby on Rails coding interview questions
• FAQs on Ruby on Rails interview questions

Basic Ruby on Rails Interview Questions With Answers

Rails is amongst the top backend frameworks for the web, and some of the world's biggest brands, such as Airbnb and Spotify, choose this framework. Most companies choose Ruby on Rails because of its libraries, user-friendly code, well-controlled framework, and frontend and backend solutions that increase developers' efficiency.

Here are Ruby on Rails interview questions that will help you brush up on vital topics.

1. What Features Make Rails a Good Option?

This is one of the frequently asked Ruby on Rails interview questions that checks your insight into various features of Rails. The following features makes Rails a good framework:

• Active record framework allows saving objects to the database. The active record Rails version identifies the column in a schema and automatically uses metaprogramming to bind it to domain objects.  
• The ability to create scaffolding or temporary code automatically.
• Meta-programming is one of the best features. Rails relies on meta-programming for heavy lifting, and Ruby is one of the best languages for meta-programming.
• It does not require much configuration if you carefully follow the naming convention.
• Rails offers three environments by default- test, development, and production.
• Rails has built-in testing that supports code called harness and fixtures.  

2. What Is ORM in Rails?

ORM stands for Object Relationship Model (ORM) in Rails. It indicates that classes are mapped to the table in the database, while objects are directly mapped to the rows in the table.

3. How Is a Module Different From a Class?

While both modules and classes use MixedCase and do not have an underscore, the key differences between the two are:

4. What Are the Types of Variables Available in Ruby Class?

This is one of the most common Ruby on Rails interview questions to gauge your understanding of the features of Ruby on Rails. The variables are as follows:

• Local variables
• Global variables
• Class variables
• Instance variables

5. What Command Creates a Controller for the Subject?

The following command allows you to create a controller for the subject.

C:\ruby\library> ruby script/generate controller subject.

6. What Is the Function of the Rails Controller?

The controller is the logical center of the application in Rails. It enables interaction between the views, users, and the model. It routes external requests to internal actions and handles URLs. The controller in Rails regulates helper modules and sessions.

7. What Is a Rails Engine?

Rails engine is one of the vital topics for Ruby on Rails interview questions. In Rails, the engines work as miniature applications providing functionality to their host applications. A Rails application serves as a supercharged engine. Rails engine enables you to wrap a specific Rails application and share it with other applications or within a larger packaged application.

8. What Is Mixin in Rails?

In Ruby, mixin offers an alternative to multiple inheritance. You can use a mixin to import modules inside another class.

9. What Role Does Mount Play in Rails Routing?

In Rails routes, mount serves the equivalent of a Unix mount and is mostly used for Rails engines. It tells the application that another app exists in that specific location.

10. What Is Garbage Collection?

As a Ruby programmer, this is one of the commonly asked Ruby on Rails interview questions. The interviewer asks this question to ensure your knowledge of freeing up memory mechanisms.

Garbage collection has the following roles in Ruby on Rails:

• It allows for pointer values removal.
• It removes the inaccessible objects from memory.
• Garbage collection creates free space in memory for other processes.

11. What Is CSRF? How Can You Protect Rails Against CSRF?

You must answer this Ruby on Rails question carefully as the interviewer checks your capability to protect the applications from hackers.

CSRF stands for Cross-Site Request Forgery (CSRF). It is a form of hacking attack where the hacker submits a page request to another website on your behalf. This process can lead to damage or reveal sensitive data.

You can protect any application from CSRF attacks by adding the "protect_from_forgery" command to your Application Controller. This causes Rails to require a CSRF token to process the request.

12. What Is Migration in Rails? How Can You Create a Rails Migration?

Migration in Rails enables Ruby to make changes to the database schema and allows you to use a VCS (version control system) to leave things synchronized with the actual code.

Rails migration is capable of the following activities:

• Rename table
• Add column
• Create table
• Drop table
• Rename column
• Change column
• Remove column and so on

You can use the following Rails code to create a migration command:

C:\ruby\application>ruby script/generate migration table_name.

Ruby on Rails Interview Questions and Answers for an Experienced Ruby Programmer

If you are an experienced Ruby programmer, you should be prepared for advanced Ruby on Rails interview questions. To ace your tech interview, you must practice the following important Ruby on Rails interview questions with answers.

1. How Do Rails implement Ajax?

You can easily submit an Ajax request in Rails. It initiates an Ajax operation as follows:

• When a user clicks on a button or a link, inducing changes to the data in the field or on a form
• When a web client uses an XMLHttpRequest, Java-script method or sends data (it can be the ID of a checkbox or the text in the entry field) linked with the trigger to an action handler on the server.
• The server-side action handler performs an action on the data and retrieves an HTML fragment to the web client.
• The client-side JavaScript (generated by Rails automatically) receives the HTML fragment and uses it for updating a particular part of the current.

2. What Is Rake in Rails?

Rake is a Ruby utility that substitutes the Unix utility "make." It is the Ruby make. Rake uses a "Rakefile" and ".rake files" to create a list of tasks. You can use Rake for normal administration tasks such as migrating the database through scripts or loading a schema into the database in Rails.

3. How Is Ruby's "Hash" Different From Active Support's "HashWithIndifferent"?

Ruby's core library has a Hash class that returns value by using a standard "= =" comparison on the keys. The stored value for a symbol key cannot be retrieved with the equivalent string. Contrastingly, the HashWithIndifferent treats both the symbol and string keys equivalent.

4. How Are Observers Different From Callbacks in Ruby on Rails?

Rails observers are similar to the callback, but they are used when the method is not directly associated with the object lifecycle. The observer has a longer life and can be attached or detached as required. For instance, you can use it to display values from a model in the UI and update models from user input.

Callbacks are methods in Rails that you can call at certain moments of an object's lifecycle. You can call it when an object is validated, updated, created, or deleted. This is short-lived. For instance, you can run a thread and give a callback when the thread terminates.

5. How Is Dynamic Scaffolding Different From Static Scaffolding?

This is one of the most frequently asked Ruby on Rails interview questions for experienced candidates. The following table enumerates the differences between the two:

6. Explain Polymorphic Association in Ruby on Rails.

Polymorphic association in Ruby on Rails allows an ActiveRecord object to connect with Multiple ActiveRecord objects.

For example, a social site where users can comment on videos, photos, links, status updates, and more is possible with the polymorphic association. Without polymorphic association, you would have to create an individual comment such as photos_comments, status_comment, and so on.

7. What Is Meta-Programming in Rails?

Rails allows meta-programming, and it gets efficient with Ruby. Meta-programming is a useful concept in Rails wherein your application creates functions or methods, or classes while it is running and can dynamically call them as well.

An example of meta-programming in action in Rails is with the route helpers. Using meta-programming, you can ask your code questions about itself during runtime, and this allows you to accomplish tasks comparatively quicker than in another language.

8. What Are the Benefits of Using Capistrano to Deploy the Rails App?

Deployment-related Ruby on Rails interview questions often form an integral part of coding interviews.

Capistrano is an ideal tool for deploying applications using deployment scripts. There are multiple tools or frameworks to minimize time, and the “cap production deploy” command is one of them. It makes everything instead of repeating the whole process on each deployment. Some key features of Capistrano are:

• You can manage your app code
• Installing new gem
• Task execution
• You can restart the sidekiq worker system commands of the operating system
• You can easily compile the assets file
• If some error occurs in the deployment process, you can roll back to the previous deployment
• It has very little or zero downtime
• Parameterize multiple environments.

Ruby on Rails Coding Interview Questions

In addition to the list of interview questions mentioned above, here are a few more coding interview questions that you may be asked during your interview:

1. What is exception handling in Ruby on Rails, and how would you do it?  
2. How to find the second max element from the database?  
3. How would you check if a specific key is present in a hash or not?  
4. How would you roll back a specific migration?  
5. How would you find only duplicates in a database table?

You can also download the Ruby on Rails interview questions and answers pdf here.

FAQs on Ruby on Rails Interview Questions

1. How do I prepare for Ruby on Rails interview questions?

You must practice your Ruby on Rails interview questions and answers to prepare well for your next interview. These will give you an idea of the interview questions that you might get asked.

If you are applying for backend Ruby developer, then you must thoroughly prepare Ruby on Rails coding interview questions. Top companies use coding challenges to test your skills in the interview. Mock interviews can also help you boost confidence and get familiar with the interview setting.

2. Are Ruby on Rails interview questions important for backend programmers?

If you are seeking a backend programmer position in Netflix, Spotify, Facebook, or any other tech company that uses Ruby, then Ruby on Rails interview questions are extremely important for you. These companies largely depend on the Rails framework for a major part of the infrastructure, including microservices and internal security applications.

3. Does Netflix use Ruby on Rails?

If this is asked as a Ruby on Rails interview question, you should know that Netflix utilizes Rails at the initial period of its streaming platform development. Presently, it depends on Ruby on Rails for a major part of the infrastructure, including microservices and internal security applications.

4. Is Ruby on Rails in demand?

Yes. In March 2022, there were over 12,000 Ruby on Rails job openings in the US (LinkedIn.com). The job market is expected to grow 13% by 2028. (zippia.com)

5. What is a Ruby on Rails developer?

Ruby on Rails developers are software engineers who use the Ruby on Rails Framework to write, develop, test, and implement software and applications.

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