Rails interview questions

Rails Interview Questions

[Qus-1]: What is Rails? And what are the components of Rails?
[Ans]: 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.
Components of Rails:

[1]: 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.

[2]: 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.

[3]: 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.

[4]: 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

[5]: 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.

[6]: 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.

[Qus-2]: Explain about RESTful Architecture.
[Ans]: RESTful: REST stands for Representational State Transfer. REST is an architecture for
designing both web applications and application programming interfaces (API’s), that’s uses
HTTP

• RESTful interface means clean URLs, less code, CRUD interface.
• CRUD means Create-READ-UPDATE-DESTROY.

You might heard about HTTP verbs, GET, POST. In REST, they add 2 new verbs, i.e, PUT, DELETE.

durgesh.tripathi2@gmail.com Page 1


There are 7 default actions, those are – index, show, new, create, edit, update, destroy.
Action VERB

index GET(used when you retrieve data from database)
show GET
new GET
create POST(used when you create new record in database)
edit GET
update PUT(used when you are updating any existing record in database)
destroy DELETE(used when you are destroying any record in database)

[Qus-3]: Why Ruby on Rails?
[Ans]: There are lot of advantages of using ruby on rails.

1. DRY Principal( Don’t Repeat Your Self): 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”

2. 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.

3. 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.
 If your plugin is specific to your application, your new plugin will be vendored
plugin.
 If you think, your plugin may be used across applications build it as a gemified
plugin.
$rails generate plugin –help //vendored plugin
$rails plugin –help //gemified plugin
 Most common plugin is AutoStripAttributes which helps to remove un-
necessary whitespaces from Active Record or Active Model attributes. Its good
for removing accidental spaces from user inputs.

4. 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.

5. 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.

6. Metaprogramming: Metaprogramming techniques use programs to write programs.

7. 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.



8. Rest Support: As explained above.

9. Action Mailer: As explained above.

[Qus-4]: What do you mean by render and redirect_to?
[Ans]: render causes rails to generate a response whose content is provided by rendering one
of your templates. Means, it will direct goes to view page.

redirect_to generates a response that, instead of delivering content to the browser, just tells it
to request another url. Means it first checks actions in controller and then goes to view page.

[Qus-5]: What is ORM in Rails?
[Ans]: 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.

[Qus-6]: How many Types of Associations Relationships does a Model have?
[Ans]: When you have more than one model in your rails application, you would need to create
connection between those models. You can do this via associations. Active Record supports
three types of associations:

 one-to-one: A one-to-one relationship exists when one item has exactly one of
another item. For example, a person has exactly one birthday or a dog has exactly
one owner.
 one-to-many : A one-to-many relationship exists when a single object can be a
member of many other objects. For instance, one subject can have many books.
 many-to-many : A many-to-many relationship exists when the first object is
related to one or more of a second object, and the second object is related to one
or many of the first object.

You indicate these associations by adding declarations to your models: has_one, has_many,
belongs_to, and has_and_belongs_to_many.

[Qus-7]: What are helpers and how to use helpers in ROR?
[Ans]: Helpers (“view 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.

[Qus-8]: What is Filters?
[Ans]: Filters are methods that run “before”, “after” or “around” a controller action. Filters are
inherited, so if you set a filter on ApplicationController, it will be run on every controller in your
application.

[Qus-9]: What is MVC? and how it Works?
[Ans]: 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, for Example your url is something like
this:
http://localhost:3000/users/new



here users is your controller and new is your method, there must be a file in your views/users
folder named new.html.erb, so once the submit button is pressed, User model will be called and
values will be stored into the database.

[Qus-10]: What is Session and Cookies?
[Ans]: Session is used to store user information on the server side. Maximum size is 4 kb.
Cookies are used to store information on the browser side or we can say client side

[Qus-11]: What is request.xhr?
[Ans]: A request.xhr tells the controller that the new Ajax request has come, It always return
Boolean values (TRUE or FALSE)

[Qus-12]: What things we can define in the model?
[Ans]: There are lot of things you can define in models few are:
1. Validations (like validates_presence_of, numeracility_of, format_of etc.)
2. Relationships(like has_one, has_many, HABTM etc.)
3. Callbacks(like before_save, after_save, before_create etc.)
4. Suppose you installed a plugin say validation_group, So you can also define validation_group
settings in your model
5. ROR Queries in Sql
6. Active record Associations Relationship

[Qus-13]: How many types of callbacks available in ROR?
[Ans:]

(1) before_validation
(2) before_validation_on_create
(3) validate_on_create
(4) after_validation
(5) after_validation_on_create
(6) before_save
(7) before_create
(8) after_create
(9) after_save

[Qus-14]: How to serialize data with YAML?
[Ans]: 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.

[Qus-15]: How to use two databases into a single application?
[Ans]: magic multi-connections allows you to write your model once, and use them for the
multiple rails databases at the same time.
• sudo gem install magic_multi_connection
• After installing this gem, just add this line at bottom of your environment.rb
require “magic_multi_connection”

[Qus-16]: Changes between the Rails Version 2 and 3?
[Ans]:



1. Introduction of bundler (new way to manage your gem dependencies)
2. Gemfile and Gemfile.lock (where all your gem dependencies lies, instead of
environment.rb)
3. HTML5 support

[Qus-17]: What is TDD and BDD?
[Ans]: TDD stands for Test-Driven-Development and BDD stands for Behavior-Driven-
Development.

[Qus-18]: What are the servers supported by ruby on rails?
[Ans]:RoR was generally preferred over WEBrick server at the time of writing, but it can also
be run by:
 Lighttpd (pronounced ‘lighty’) is an open-source web server more optimized for speed-
critical environments.
 Abyss Web Server- is a compact web server available for windows, Mac osX and Linux
operating system.
 Apache and nginx

[Qus-19]: What do you mean by Naming Convention in Rails.
[Ans]:
 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 OrdersController 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.
Summary
1. Model Naming Convention

Table: orders
Class: Order
File: /app/models/order.rb
Foreign key: customer_id
Link Table: items_orders

2. Controller Naming Convention

Class: OrdersController
File: /app/controllers/orders_controller.rb
Layout: /app/Layouts/orders.html.erb

3. View Naming Convention

Helper: /app/helpers/orders.helper.rb
Helper Module: OrdersHelper



Views: /app/view/orders/…(list.html.erb for example)

4. Test Naming Convention

Unit: /test/unit/order_test.rb
Functional: /test/functional/orders_controller_test.rb
Fixtures: /test/fixtures/orders.yml

[Qus-20]: What is the log that has to seen to check for an error in ruby rails?
[Ans]: 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.

[Qus-21]: How you run your Rails application without creating databases?
[Ans]: You can run your application by uncommenting the line in environment.rb
path=> rootpath conf/environment.rb
config.frameworks- = [action_web_service, :action_mailer, :active_record]

[Qus-22]: How to use sql db or mysql db without defining it in the database.yml?
[Ans]: You can use ActiveRecord anywhere

require “rubygems”
require “active_record”
ActiveRecord::Base.establish_connection({
:adapter=> ‘postgresql’, :user=>’foo’, :password=> ‘abc’, :database=>’whatever’})

[Que-23]: GET and POST Method?
[Ans]: 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.


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