Latest Top 20 Ruby On Rails Interview Questions With Answers

1. What Is Rails?
Rails is a extremely productive web-application framework written in Ruby language by David Hansson.
Rails are an open source Ruby framework for developing database-backend web applications.
Rails include everything needed to create a database-driven web application using the Model-View-Controller (MVC) pattern.

2. Why Ruby On Rails?
There are lot of advantages of using ruby on rails.
DRY Principal( Don’t Repeat Yourself): It is a principle of software development aimed at reducing repetition of code. “Every piece of code must have a single, unambiguous representation within a system”
Convention over Configuration: Most web development framework for .NET or Java force you to write pages of configuration code. If you follow suggested naming conventions, Rails doesn’t need much configuration.
Gems and Plugins: RubyGems is a package manager for the Ruby programming language that provides a standard format for distributing ruby programs and library.
Plugins: A Rails plugin is either an extension or a modification of the core framework. It provides a way for developers to share bleeding-edge ideas without hurting the stable code base. We need to decide if our plugin will be potentially shared across different Rails applications.
Scaffolding: Scaffolding is a meta-programming method of building database-backend software application. It is a technique supported by MVC frameworks, in which programmer may write a specification, that describes how the application database may be used. There are two type of scaffolding:
-static: Static scaffolding takes 2 parameter i.e your controller name and model name.
-dynamic: In dynamic scaffolding you have to define controller and model one by one.
Rack Support: Rake is a software task management tool. It allows you to specify tasks and describe dependencies as well as to group tasks in a namespace.
Metaprogramming: Metaprogramming techniques use programs to write programs.
Bundler: Bundler is a new concept introduced in Rails 3, which helps you to manage your gems for application. After specifying gem file, you need to do a bundle install.
Rest Support.
Action Mailer

3. What Is Orm In Rails?
ORM tends for Object-Relationship-Model, where Classes are mapped to table in the database, and Objects are directly mapped to the rows in the table.

4. What Are The Various Components Of Rail?
Action Pack: Action Pack is a single gem that contains Action Controller, Action View and Action Dispatch. The “VC” part of “MVC”.
Action Controller: Action Controller is the component that manages the controllers in a Rails application. The Action Controller framework processes incoming requests to a Rails application, extracts parameters, and dispatches them to the intended action.
Services provided by Action Controller include session management, template rendering, and redirect management.
Action View: Action View manages the views of your Rails application. It can create both HTML and XML output by default.
Action View manages rendering templates, including nested and partial templates, and includes built-in AJAX support.
Action Dispatch: Action Dispatch handles routing of web requests and dispatches them as you want, either to your application or any other Rack application. Rack applications are a more advanced topic and are covered in a separate guide called Rails on Rack.
Action Mailer: Action Mailer is a framework for building e-mail services. You can use Action Mailer to receive and process incoming email and send simple plain text or complex multipart emails based on flexible templates.
Active Model: Active Model provides a defined interface between the Action Pack gem services and Object Relationship Mapping gems such as Active Record. Active Model allows Rails to utilize other ORM frameworks in place of Active Record if your application needs this.
Active Record: Active Record are like Object Relational Mapping (ORM), where classes are mapped to table, objects are mapped to columns and object attributes are mapped to data in the table.
Active Resource: Active Resource provides a framework for managing the connection between business objects and RESTful web services. It implements a way to map web-based resources to local objects with CRUD semantics.
Active Support: Active Support is an extensive collection of utility classes and standard Ruby library extensions that are used in Rails, both by the core code and by your applications.

5. What Are Helpers And How To Use Helpers In Ror?
Helpers are modules that provide methods which are automatically usable in your view. They provide shortcuts to commonly used display code and a way for you to keep the programming out of your views. The purpose of a helper is to simplify the view.

6. What Is Mvc? And How It Works?
MVC tends for Model-View-Controller, used by many languages like PHP, Perl, Python etc. The flow goes like this:
Request first comes to the controller, controller finds and appropriate view and interacts with model, model interacts with your database and send the response to controller then controller based on the response give the output parameter to view.

7. What Is Request.xhr?
A request.xhr tells the controller that the new Ajax request has come, It always return Boolean values (TRUE or FALSE)

8. How Many Types Of Callbacks Available In Ror?
before_validation
before_validation_on_create
validate_on_create
after_validation
after_validation_on_create
before_save
before_create
after_create
after_save

9. What Is Tdd And Bdd?
TDD stands for Test-Driven-Development and BDD stands for Behavior-Driven-Development.

10. How To Serialize Data With Yaml?
YAML is a straight forward machine parsable data serialization format, designed for human readability and interaction with scripting language such as Perl and Python.
YAML is optimized for data serialization, formatted dumping, configuration files, log files, internet messaging and filtering.

11. What Do You Mean By Naming Convention In Rails.
Variables: Variables are named where all letters are lowercase and words are separated by underscores. E.g: total, order_amount.
Class and Module: Classes and modules uses MixedCase and have no underscores, each word starts with a uppercase letter. Eg: InvoiceItem
Database Table: Table name have all lowercase letters and underscores between words, also all table names to be plural. Eg: invoice_items, orders etc
Model: The model is named using the class naming convention of unbroken MixedCase and always the singular of the table name.
For eg: table name is might be orders, the model name would be Order. Rails will then look for the class definition in a file called order.rb in /app/model directory. If the model class name has multiple capitalized words, the table name is assumed to have underscores between these words.
Controller: controller class names are pluralized, such that Orders Controller would be the controller class for the orders table. Rails will then look for the class definition in a file called orders_controlles.rb in the /app/controller directory.

12. How Many Types Of Relationships Does A Model Has?
has_one
belongs_to
has_many
has_many :through

13. Get And Post Method?
GET is basically for just getting (retrieving) data, whereas POST may involve anything, like storing or updating data, or ordering a product, or sending E-mail.

14. What Is The Log That Has To Seen To Check For An Error In Ruby Rails?
Rails will report errors from Apache in log/apache.log and errors from the ruby code in log/development.log. If you having a problem, do have a look at what these log are saying.

15. Difference Between Render And Redirect?
render example: render :action, render :partial etc. redirect example: redirect_to :controller => ‘users’, :action => ‘new’

16. What Is Bundler?
Bundler is a new concept introduced in Rails3, which helps to you manage your gems for the application. After specifying gems in your Gemfile, you need to do a bundle install. If the gem is available in the system, bundle will use that else it will pick up.

17. What Are The Components Defined In The Model From Mvc Architecture?
The components involved in defining the model are as follows:
Validations: this is one of the very essential components and it defines the validations that are being put up on the input type of stream like validate_presence_of, format_of, etc.
Relationship: this is another type of component that describe the relationship between different types of components and it shows the relationship in the form of has_one, has_many, etc.
Callbacks: this is essential when it comes to respond after the failure and it allows the application to have certain functionality during failure. This can be given as before_save, after_save, etc.
Validation group settings: allow users to define the installed plugin settings.
Active record association relationship: allows current records to be actively having the relationship between one another.

18. Render Vs. Redirect_to In Ruby On Rails ?
render will render a particular view using the instance variables available in the action.
For example if a render was used for the new action, when a user goes to /new, the new action in the controller is called, instance variables are created and then passed to the new view. Rails creates the html for that view and returns it back to the user's browser. This is what you would consider a normal page load.
redirect_to will send a redirect to the user’s browser telling it to re-request a new URL as 302 redirect response. Then the browser will send a new request to that URL and it will go through the action for that URL, oblivious to the fact that it was redirected to. None of the variables created in the action that caused the redirect will be available to the redirected view. This is what happens when you click on ‘Create’ in a form and the object is created and you’re redirected to the edit view for that object.

19. What Is The Difference Between Delete And Destroy ?
The delete method essentially deletes a row (or an array of rows) from the database. Destroy on the other hand allows for a few more options. First, it will check any callbacks such as before_delete, or any dependencies that we specify in our model. Next, it will keep the object that just got deleted in memory; this allows us to leave a message saying something like “ 'Object_name' has been deleted.” Lastly, and most importantly, it will also delete any child objects associated with that object!

20. What Is The Flash?
The flash is a special part of the session which is cleared with each request. This means that values stored there will only be available in the next request, which is useful for storing error messages etc. It is accessed in much the same way as the session, like a hash.
flash is a object of Actiondispatch class.