ROR Questions

Question 1

Rails CRUD

Answer 1

Create, Read, Update, Destroy //routes.rb resources :articles

Question 2

WHAT IS EAGER LOADING?

Answer 2

Eager loading is a great optimization strategy to reduce the number of queries that are made against the DB. clients = Client.includes(:address).limit(10) clients.each do |client| puts client.address.postcode end

Question 3

What is a class? How and When to create?

Answer 3

A class is the blueprint from which individual objects are created. class Customer end

Question 4

What is an object?

Answer 4

Is an instance of the class. You can create objects in Ruby by using the method new of the class. cust1 = Customer.new The initialize method is a special type of method, which will be executed when the new method of the class is called with parameters def initialize(id, name, addr) @cust_id=id @cust_name=name @cust_addr=addr end

Question 5

How would you declare and use a constructor in Ruby?

Answer 5

Constructors are declared via the initialize method and get called when you call on a new object to be created. Order.new class Order def initialize(meal) @meal = meal end end

Question 6

When to use a symbol?

Answer 6

Used as keys in Hashes. Used on attr_accessor.

Question 7

How would you create getter and setter methods in Ruby?

Answer 7

Setter and getter methods in Ruby are generated with the attr_accessor method.

Question 8

What is polymorphic association?

Answer 8

With polymorphic associations, a model can belong to more than one other model, on a single association.

Question 9

What is a Proc?

Answer 9

short for procedures, act similar to blocks, but can be saved as variables and reused. Think of them as blocks you can call over and over again on multiple arrays. square = Proc.new do |n| n ** 2 end

Question 10

What is a Block?

Answer 10

a block is like a proc that can’t be saved. array = [1, 2, 3, 4] array.collect! do |n| n ** 2 end

Question 11

What are lambdas?

Answer 11

Anonymous function.

Question 12

What is the difference between a class and a module?

Answer 12

A module cannot be subclassed or instantiated, and modules can implement mixins.

Question 13

What are the three levels of method access control for classes and what do they signify? What do they imply about the method?

Answer 13

Public methods can be called by all objects and subclasses of the class in which they are defined in. Methods are public by default except for initialize, which is always private.

A protected method can be invoked only by objects of the defining class and its subclasses. Access is kept within the family.

Private methods cannot be accessed, or even viewed from outside the class. Only the class methods can access private members.

Question 14

Explain what functional testing is:

Answer 14

Functional testing in Rails allows you to test the response of various actions contained in a controller.

Question 15

The initialize method:

Answer 15

class Box

def initialize(w,h)

@width, @height = w, h

end

end

Question 16

Class Inheritance:

Answer 16

Inheritance allows us to define a class in terms of another class.

existing class is called the base class or superclass.

new class is referred to as the derived class or sub-class.

eg:

ArticlesController

ApplicationController

Question 17

Methods Overriding:

Answer 17

You can do so simply by keeping the method name same and overriding the functionality of the parent class method.

Question 18

Abstraction

Answer 18

The abstraction is simplifying complex reality by modeling classes appropriate to the problem.

Question 19

Encapsulation

Answer 19

hides the implementation details of a class from other objects.

Question 20

What is the constructor?

Answer 20

The purpose of the constructor is to initiate the state of an object. The constructor in Ruby is called initialize. Constructors do not return any values.

class Being

def initialize

puts “Being is created”

end

end

Being.new