Rails Basics

Question 1

What is Rails

Answer 1

open source web application framework written in Ruby.

Question 2

Active Record Pattern

Answer 2

a database table is represented as a class; each row of the tables is created/updated by an object instance.

Question 3

Convention over Configuration

Answer 3

A software design that decreases the number of decisions to be made by developers
E.g. Rails automatically render views with names that correspond to valid routes.

Question 4

What is a Framework?

Answer 4

A framework is a program or code library that writes most of your application for the developer.

Question 5

What is MVC?

Answer 5

Model: Application data.

View: Presentation layer

Controller: Processes and responds to events

Question 6

How does MVC work?

Answer 6

Request first comes to the controller, controller finds the 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

Question 7

Explain RESTful Architecture

Answer 7

REST = REpresentational State Transfer

It uses HTTP methods GET, PUT, POST, or DELETE

RESTful interface means clean URLs, less code.

Question 8

Why Rails?

Answer 8

DRY Principal( Don’t Repeat Yourself)

Convention over Configuration

Gems

Question 9

What is the ORM of rails?

Answer 9

ORM stands for Object-Relationship-Model, where classes are mapped to tables in the database, and objects are directly mapped to the rows in the table

Question 10

What Associations Relationships does a Model have?

Answer 10

one-to-one: exists when one item has exactly one of another item.

one-to-many: exists when a single object can be a member of many other objects.

many-to-many: 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.

belongs_to
has_one
has_many
has_many :through
has_one :through
has_and_belongs_to_many

Question 11

What is the Ruby naming convention for methods?

Answer 11

Lowercase names that may be followed by digits, underscores, letters, e.g. paint or close_the_door

Question 12

What are Instance and Class variables?

Answer 12

Instance variables(@): the data varies with each instance of the object. @i = 1

Class variables(@@): “static variables”, shared across all instances of a class.  
@@i = 1

Question 13

What is the difference between empty , nil and blank?

Answer 13

Nil: used on any object and is true if the object is nil

Empty: can be used on strings, arrays and hashes and returns true if:
String length == 0;
Array length == 0;
Hash length == 0;

.blank? evaluates true on strings which are non-empty but contain only whitespace.

Question 14

What is a destructive method?

Answer 14

It is a method that alters the attribute of an object.
Example:
myabcs = [‘a’, ‘b’, ‘c’] #myabcs is of type Array
myabcs.reverse! #this method altered the object
p myabcs #outputs
#[[“c”,”b”,”a”]

Question 15

What are the variable scopes?

Answer 15

Local variables are local to the code construct in which they are declared. eg: method, loop.
must begin with either an underscore or a lower case letter
i = 5

Global variables accessible from anywhere in the Ruby program.
$speed = 10

Class variable is shared amongst all instances of a class. Only one variable value exists for all objects. If one object instance changes the value of the variable, that new value will change for all other object instances.
@@i = 5

Instance variables are local to specific instances of an object.
@i = 5

Ruby constants are values which, once assigned a value, should not be changed.
GRAVITATIONAL_CONST = 6.67

Question 16

Name a few object oriented concepts in Ruby.

Answer 16

Classes, Objects, Inheritance, Singleton methods, polymorphism(accomplished by overriding and overloading) are some object oriented concepts supported by Ruby

Question 17

Provide an example if how an iterator is used?

Answer 17

times
Iterate through the block 3 times, n starts at 0 and ends at 2 and is incremented by 1 each time. n is the block variable. 
3.times do |n|
puts n
end

upto
Iterate through the block 3 times, starting at 1 and ending at 3, each time incrementing by 1. n is the block variable.
1.upto(3) do |n|
puts n
en

downto
Iterate through the block 3 times, starting at 3 and ending at 1, each time decrementing by 1. n is the block variable.
3.downto(1) do |n|
puts n
end

Question 18

When to use Load vs Require in Ruby?

Answer 18

Require loads the file only once, while load loads it every time it is called
Use load rather than require if you need to force something to reload (e.g. a web server or a test server)
Load takes in a file’s full name path such as:
load “/path/to/file.rb”

Question 19

Argument vs Parameter

Answer 19

The parameter is what is declared/ defined in a method or a class
An argument is the value that is passed when calling the function or instantiating the class. Example: 
class Person
    attr_accessor :name, :age
    def initialize(name = '', age = 0)
        self.name = name
        self.age = age

Question 20

RESTfull Resources

Answer 20

GET	/photos	photos#index	
GET	/photos/new	photos#new
POST	/photos	photos#create
GET	/photos/:id	photos#show
GET	/photos/:id/edit	photos#edit
PATCH/PUT	/photos/:id
DELETE	/photos/:id