Ruby on Rails interview questions

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Ruby on Rails interview questions

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Question

What is MVC?

Answer

Model-View-Controller (MVC) is a design pattern for structuring software applications. The MVC pattern separates application logic from the user interface. MVC stands for Model, View, and Controller, the three main components of the MVC application architecture. The Model is a layer between a database and an application that stores business logic related to a specific entity. A View is a visualization of the attached Model state. And controllers are responsible for accepting requests, finding appropriate actions and returning responses back.

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Question

What is ORM in Rails?

Answer

ORM is Object-Relationship-Model. It means that data model Classes are mapped to appropriate tables in the application database. And Objects are directly mapped to the rows in the table.

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Question

What is Ruby Gems?

Answer

It's a package manager in Ruby. It allows you to easily download, install and manage gems on your application.

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Question

What things we can define in the Rails model?

Answer

There are lot of things you can define in models. For example:

Model properties and primary key
Validation rules
Relationships with other models like: "one to one", "one to many" and "many to many"
Callbacks
Custom database queries

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Question

What is the difference between -%> and %> in Rails?

Answer

The extra dash makes ERB not output the newline after the closing tag.

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Question

What are helpers and how to use helpers in Rails?

Answer

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.

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Question

What is bundler in Rails?

Answer

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.

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Question

What is migrations in Rails?

Answer

Migrations is organized way to manage database changes. Migrations are stored in files as special classes which allows to keep track of them in a repository. Miagrations also allow to manage database of different enviroments like production, staging, testing, development etc. Active Record tracks which migrations have already been run so all you have to do is update your source and run rake db:migrate

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Question

What is the difference between form_for and form_tag?

Answer

form_tag and form_for both are used to submit the form and it’s elements. The main difference between these two is the way of managing objects related to that particular model is different. You should use “form_for” tag for a specific model. And form_tag creates a form as a normal form without any model backed and has normal fields.

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Question

What is scaffolding in Rails?

Answer

Scaffolding in Ruby on Rails refers to the auto generation of a simple set of a model, views and controller usually for a single table.

For example:rails generate scaffold UserThis will create a full CRUD (create, read, update, delete) web interface for the Users table.

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Question

How to use nested routes in Rails?

Answer

The easiest way to create a nested route, is to use the :has_many keyword like that:

# /config/routes.rb
map.resources :categories, :has_many => :products

# and the correspondent project resource
map.resources :projects

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Question

What is observer in in Rails?

Answer

If you want to observe changes in model attibutes and respond to those changes it's recommended to use a separate Observer class. Model specific event handling is much cleaner this way and will avoid models from polluting the model by un-necessary methods.

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