Ruby on rails interview questions and Answers

Ruby on Rails is an open-source web development tool that is built on top of Ruby programming language. Designed around productivity and simplicity, this framework gives developers a structure for writing code for building websites and web applications.

David Heinemeier Hansson

• Integrated application
• Default configuration saves a lot of time and work.
• Great ecosystem helps you find online tools & support.
• Active development status keeps introducing fixes & adding features.
• Testing frameworks are strong.

6.0.0.rc1

Class libraries consist of many domains including thread programming, data types, and various domains.

• In Variables, all letters must be lowercase and words should be separated by underscores.
• Modules and Classes use MixedCase and no underscore is required. Each word must start with uppercase.
• The database table name should have a mix of lowercase and underscore, and all names should be in the plural form.
• Model is represented by MixedCase and has singular table name.
• The names of Controller are in plural form.

ORM indicate that classes are mapped to the table in the database, and objects are mapped to the rows.

False indicates a Boolean datatype, and Nil is not a data type and it have an object_id 4.

App/controllers: A Controller handles the web request from the user. Rails search the controller sub-directory for controller classes.

App/helpers: This sub-directory holds helper classes that are used to assist the controller classes.

Symbol belongs to the immutable objects category whereas Strings are mutable objects. Both symbol and strings act similarly, but they differ in behavior. The difference lies mainly in the memory object_id and process tune when you use them together.

It is the ORM layer that is supplied with Rails and it follows the ORM model as follows:

• Map Table to classes
• Map Rows to objects
• Map Columns to object attributes

Ajax-powered pages retrieve the page from the server. This page is unlike other web pages where you have to refresh the page to see the latest update. Rails trigger Ajax in the following ways:

• When a user clicks a button, he or she induces changes in the form or field.
• A Java-script method sends trigger-linked data to a handler on the server.
• The server-side handler works on the data and retrieves an HTML to the web client.
• The client-side JavaScript receives the HTML and updates the current.

Use the following command for creating a controller:

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

The Rails controller is the center of the application that facilitates the interaction between users, views, and model. It also routes external requests to internal actions and handles URL. It also regulates helper modules and sessions.

Rails Migration enables to make changes to the database, allowing it to use a version control system for synchronizing things with actual code. It can perform the following functions:

• Create, drop, rename table
• Add, rename, change and remove a column

self.up is used for migrating to a new version, while self.down is used to roll back changes.

It is a form of attack where a hacker submits a request on your behalf to a website, causing damage or revealing sensitive data. In order to protect from attacks, you must add “protect_from_forgery” to your ApplicationController. This will require a CSRF token to process the request.

You can run your application by uncommenting in environment.rb

path=> rootpath conf/environment.rb

config.frameworks = [ action_web_service, :action_mailer, :active_record]

Observers are the same as Callback, but they are used when the method is not directly associated with the object. The observer lives longer, and can be detached or attached at any time.

Callbacks are methods that can be called only at certain moments of an object’s lifecycle. Callbacks live shorter.

It is a Ruby Make or a utility that is used for administrative tasks such as migrating the database through scripts and loading schema into the database. In Rails, it substitutes the Unix utility ‘make’ and uses ‘Rakefile’ and ‘.rake files’ to build up task lists.

Dynamic Scaffolding

• Automatically creates content and UI at runtime.
• Facilitates the generation of new, delete, and edit methods in the application.
• Does not require the database to be synchronized.

Static Scaffolding

• Requires manual entry to create data within fields.
• Does not require a generation to take place.
• Requires database to be migrated.

• It enables removal of pointer values that are left behind after the program execution ends.
• It releases the programmer from tracking objects that get created dynamically on runtime.
• It facilitates the removal of distant objects from the memory so that other processes can use the memory.

Redirect is used to issue the error message when the page is not found in the browser. This function tells the browser to issue a new request.

Render is used to make the content and it only works when the controller is being set up with the variables that require rendering.

It is a template that produces JavaScript. This javaScript then runs in an eval block in response to an AJAX request. Sometimes, this template is also used to define JavaScript, Prototype and helpers offered by Rails.

A call to super() initiates the parent method without any disputes.

A call to super initiates the parent method with the same disputes that were passed to the child. An error will occur if the arguments passed to the child do not match with the parent method.

Float is used when the function changes constantly.

Dig is used when you want to show a float in decimal digits.

Max is used when there is a need of Float.

Mainly four types of variables are available in Ruby Class - local variables, global variables, class variables and instance variables.

Ruby

• There are options for carrying out an action.
• It a reflective and object-oriented programming language.
• Used for functional programming.
• Frequent updates.

Python

• There is one specific way to carry out an action.
• It is a high-level and general purpose language.
• Used for scientific programming.
• Fewer updates.