Top 25 Ruby on Rails Interview Questions & Answers 2022

Ruby on Rails Interview Questions & Answers

Are you interested in a programming job focusing mainly on Ruby and Rails? If yes, we have something for you. This article will look at some of the questions you should expect in a Ruby and Rails Interview. Take a look at the following:

1. What is Ruby on Rails?

Ruby on Rails is open-source software and web application framework written in Ruby, one of the major programming languages. It comprises two words, Ruby and Rails, which have different meanings. Ruby is the programming language, while rails is the framework used in web application building. The former( Ruby) is object-oriented and is inspired by Ada, Basic, Lisp and Eiffel.

2. What are Some of the Naming Conventions in Rails?

There are several different naming conventions in Rails. All the letters must be lowercase when declaring variables, and underscores must separate words. For the database table, the table name must have a lowercase number and an underscore between the words. The table names must also be in plural form. Additionally, the model is presented by unbroken MixedCase while controller class names must exist in plural form. Lastly, modules and classes use mixed cases with no underscore. Each word has to start with an uppercase letter.

3. What are Some of the Positive Aspects of Rails?

Rails has several positive features: Rails can automatically create temporary code and comes with three default environments: testing, development, and production. Even though it is capable of code generation, it also relies on metaprogramming for heavy lifting purposes. This is partly because it is one of the best languages for metaprogramming. Rails also support built-in testing thanks to harnesses and fixtures that allow testing and execution of test cases. Other features include an active record framework and priority on convention over configuration.

4. How Do Rails Implement Ajax?

Ajax allows the retrieval of web pages from the server, saving users the stress of refreshing the page for new information. Rails are capable of triggering an Ajax operation in several ways. First, a user can induce changes to the data by clicking on a link or button, popularly known as trigger fire. Also, JavaScript, which is automatically generated by Rails, can receive the HTML fragment, which is used to update new information. The web client can also call the server or the server-side to retrieve an HTML fragment to the web client.

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5. What is the Difference Between Dynamic and Static Scaffolding?

There are several notable differences between dynamic and static scaffolding. Dynamic scaffolding automatically creates content and user interface at runtime, whereas static scaffolding depends on manual entry to generate data and related fields. The former also allows for new, delete and edit methods for application use, whereas static scaffolding does not allow for such generation. Lastly, dynamic scaffolding does not require the synchronization of a database, while static scaffolding requires its migration.

6. Can You Please Explain Class Library

Ruby has class libraries that have several domains. Some of the common types are thread programming, data types, different domains, among many others. They are essential since they offer flexible abilities/capabilities during high-level abstraction allowing programmers or users to develop powerful Ruby scripts to be used in several problem domains. Some domains with relevant class libraries are text processing, CGI programming, network programming and GUI programming. All these are useful for any Ruby on Rails programmer.

7. Do You Know How to Denote Class Variables in Ruby?

Several notations should be observed when denoting class variables in Ruby. First, a constant must begin with an uppercase letter and shouldn’t be defined inside a method. Secondly, a local has to begin with an underscore or lowercase letter. A class variable must also start with double @@ and be initialized before using the method definition. Lastly, a global variable should begin with the dollar sign. Generally, an uninitialized global variable is usually equalized as Nil in value and should raise a warning. All in all, it can be referred anywhere in the program.

8. Do You Know the Function of Garbage Collection in Ruby and Rails?

Ruby and Rails has a garbage collection feature that plays several functions. Primarily, it allows for the removal of pointer values usually left behind when program execution comes to a halt. It further frees the programmer from tracking objects creates dynamically on runtime, thus saving time and making work easier. It also removes any inaccessible objects from memory, allowing other processes to use the same memory. It, therefore, has several advantages that many Ruby on Rails programmers are continually thankful for.

9. Do You Know the Roles of a Rails Controller?

A Rails Controller plays several essential roles. However, it is first necessary to mention that it is the logical centre of the application. Therefore, its primary function is to permit or facilitate interaction between the users, views and the model. It also performs various other activities such as regulating sessions hence passing the impression of ongoing interactions with applications to users. It also regulates helper modules, thus allowing viewing of templates without code bulking and routes external requests to internal actions, thus handling URL exceedingly well.

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10. Do You Know the Difference Between String and Symbol?

Both strings and symbols work in the same way, just that they differ entirely in behaviour. This difference normally comes in the object_id memory and process tune whenever these two are used together. The symbol is usually classified as an immutable object, whereas strings are often grouped as mutable objects. Other differences are: symbol is more of a string than a variable;  only one copy of the symbol has to be created, unlike for strings, and symbols are generally used as corresponding enums in Ruby.

11. What Do You Understand by Rails Migration?

Rails Migration is an essential tool in Ruby on Rails that allows the framework to make changes to the application’s database schema. Instead of managing query scripts, it allows users to define these changes in a more specific language, known as Domain Specific Language or DSL. Given that the code applied is usually database-independent, one can easily move an app to a different or new platform. It is also pretty convenient since, unlike other programming languages and frameworks, a developer-only needs to update and run ‘rake migrate’ when a team member makes a schema change.

12. What Can Rails Migration Do?

Rails Migration is capable of performing a number of functions. It can create tables, remove columns, rename tables, add columns, drop tables, rename columns and change columns, among many other things. All in all, it permits the modification of database schema, which allows users to use a version control system and leave things synchronized with the existing and actual code. Creating a migration is relatively easy since all one needs is to come up with the correct command, specifying the intent.

13. Can You Tell Us the Difference Between Observers and Callbacks

Even though rail observers are slightly similar to the rail callbacks, they differ in regards to object lifecycles. Rails observers are customarily used when a given method does not directly associate with the object’s lifecycle. The observer also has a longer lifespan and can be attached or detached as a programmer pleases. On the other hand, rails callbacks are methods that can be commanded at different moments of an object’s lifecycle. Such moments include during validation, update or deletion of an object. They are, therefore, relatively short-lived as compared to their counterparts.

14. Do You Know the Difference Between Redirect and Render in Ruby on Rails?

Redirect is usually used to pass across an error message when a page is not issued or cannot be fetched by a browser. It, therefore, directs the browser to not only process but also issue a new request. On the other hand, action rendering is generally used by the action controller in instances where there is no unique specification. Render, therefore, only works when the controller is being established or set up with the variables being rendered. There is, therefore, a considerable difference between these two functions.

15. What Do You Know about RJs in Rails?

RJS is a template that is similar to an HTML.erb file. It usually generates JavaScript to be executed by the browser. This process normally follows an AJAX request and can be fully defined as Ruby to JavaScript. An RJS file, therefore, has an .RJs extension that combines both Ruby code and JavaScript, allowing rails developers to use Ruby and come up with unique creations. It is also worth noting that this template is not nowadays users in the Rails ecosystem as Server-generated JavaScript responses are now preferred over it.

16. Do You Know the Different Types of Variables Available in Ruby Class?

There are four different types of variables in the Ruby Class, namely global, class, instance and local variables. An instance variable is usually declared in a class but outside the blocks. A local variable has a local scope, given that it is declared within the programming block or subroutines. On the other hand, a global variable has a global scope making it visible throughout the program unless one shadows it. All global variables in existence are generally known as the global environment. Lastly, class variables are used to declare variables within a given class.

17. What is the Difference Between Procs and Blocks in Ruby on Rails?

A proc refers to a block of code stored on a local variable, whereas blocks are functions that are usually passed in methods. There are a number of notable differences between Procs and Blocks in Ruby on Rails. However, the main difference is that whereas procs are objects, blocks are not. Also, proc can be stored into a variable while a block cannot. Also, only one block can appear on an argument list, which is not the same for Procs. Those are just but a few differences that one should know.

18. Can You Differentiate Gem and Plugin in Ruby?

Gems, also known as RubyGems, is a package manager that allows easier distribution of Ruby programs and libraries by offering a standard distribution program. The package manager also offers a tool for managing the easy installation of gems and distribution servers. A plugin is also a Ruby code installed in an application folder and can only be used by a specific application. It can either be a modification or extension of the primary framework, allowing developers to share ideas without hurting the codebase. The main difference between these two is that a plugin is deployed with the application, whereas a gem needs to be installed on the system.

19. Can You Tell the Difference Between Single and Double Quotes?

The main difference between single and double quotes is that single quotes are unable to print escape sequences directly, which can be achieved by double-quotes. Ruby commonly uses double-quoted strings for string interpretation. It is also worth noting that single quotes strings can’t process ASCII codes and are incapable of string interpolation. In Ruby, string interpolation refers to bringing different strings together through the + operator. It only works where double quotes are involved.

20. Mention Some of the features of Ruby that You Know

Ruby has a number of features making it unique. This programming language has a free format, meaning that one can begin writing from any line or column. It is also case sensitive, and therefore, both the uppercase and lowercase letters must be specific. Ruby has statement delimiters, which means one must use a semicolon to separate several statements on one line, except at the end of the line. The interpreter must also ignore anything followed by an unquoted # at the end of the line.

21. Can You Mention Some of the Limits of Ruby on Rails

Ruby on Rails has a number of limits that explain why it is not as popular as other frameworks among senior or professional developers. Most people find it too rigid in the end and therefore have to abandon it as it uses more than one database. It also does not support many features, making it unusable for most programmers and DevOps engineers. This is partly caused by its connection to more than one database server at a time and the presence of foreign keys in databases.

22. Can You Tell Us the Advantages of Using Ruby on Rails?

Ruby on Rails comes with several advantages despite some of the limitations I mentioned before. First, it is open source and therefore entirely free for anyone who would like to code. Programmers also get a chance to write code acting on actual code and not data. This programming language makes it easy to manage changes as one can easily modify existing code or add new site features. It is, therefore, the best framework for long-term projects, thanks to its predictability and stability. Lastly, this framework is secure as it has a number of default security measures.

23. Mention the Different Components of Rails

Rails , being a framework, has a number of components that every Ruby on Rails developer should be aware of. These include ActiveSupport, ActiveModel, ActiveRecord, ActionMailer and ActionPack. These components are also brought about by the fact that this framework is normally made up of other independent or standalone frameworks. The ActiveSupport component contributes language extension, utilities and several other diverse functions to Ruby. ActiveModel, on the other hand, allows Action Pack Helpers to interact with Ruby objects.

24. What are Some of the Projects that Require Ruby on Rails?

Ruby on Rails offers a platform that can best create online stores. If you need an online store that can support sophisticated or high-level browsing and purchase option, then this is the best framework to turn to. It can also be used to create quality stock marketing platforms, which are more or less similar to online stores. A developer can further use this framework to create social networking sites. Lastly, owing to its easy building features, one can use it to create different Saas solutions. Ruby on Rails clearly has a wide application.

25. Why is Ruby on Rails Considered One of the Most Productive Frameworks For Developers?

Using Ruby on Rails for building web applications allows speedily development of features, making it one of the most productive frameworks since it can easily combine different 3rd party software libraries. This is one of the most significant advantages of this web application framework. Other advantages are its cost-effectiveness given that it is a free and open-source framework; security owing to the default security measures, flexibility given that it uses both front and backend abilities, and consistency thanks to the necessary file storage and conventions.


We have come to the end of our article. These are some of the most common technical questions you should expect in a Ruby on Rails Interview. Make sure that you are conversant with this framework before setting foot in any related interview.

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