Ruby Basics

Question 1

abstraction

Answer 1

Abstraction ensures that as users, we’re far removed from what’s happening “under the hood”

Question 2

abstraction of ruby

Answer 2

Ruby is written in C, which translates to Assembly Language, which translates to machine language to translate 0s and 1s into something the computer understands.

Question 3

Domain Specific Languages (DSL’s)

Answer 3

is a computer language specialized to a particular application domain. A higher level language based on a lower level. Rails or Rspec written in Ruby.

Question 4

tab function

Answer 4

set to 2 spaces and indenting should be set to use spaces

Question 5

sign

Answer 5

means anything after it, on the same line, is a comment

Question 6

snake_case

Answer 6

When you define or initialize a method, variable, or file.

# Naming a file
this_is_a_snake_cased_file.rb

# Assigning a variable
forty_two = 42

# Defining a method
def this_is_a_great_method
  # do stuff
end

Question 7

constant

Answer 7

When you want to represent a value that will not change in your Ruby program, you define a constant variable, often referred to as a constant. In Ruby, constants are denoted with all uppercase letters.

# Constant declaration
 FOUR = 'four'
 FIVE = 5

Question 8

do/end blocks, prefer { }

Answer 8

when the entire code expression fits on one line.

# Multi-line
  [1, 2, 3].each do |i|
    # do stuff
  end

  # Does the same thing in single line
  [1, 2, 3].each { |i| # do stuff }

Question 9

CamelCase

Answer 9

naming your classes you will use CamelCase formatting. CamelCase uses no spaces and capitalizes every word.

# Class naming
  class MyFirstClass
  end

  class MySecondClass
  end

Question 10

API

Answer 10

API is an acronym for application programming interface, and is a somewhat overloaded term that can refer to both how applications talk to each other, as well as documentation. Just remember, if someone says “Did you take a look at the Array API?”, they’re talking about the Ruby docs documentation for the Array class. But if someone says “What’s the Twitter API?”, they’re talking about the programmatic interface to Twitter’s services.

Question 11

mkdir

Answer 11

create a new directory

Question 12

cd

Answer 12

change directory

Question 13

touch

Answer 13

create a new file

Question 14

rm

Answer 14

remove a file (delete)

Question 15

cd ..

Answer 15

To navigate out of the current folder to the one above

Question 16

rmdir

Answer 16

remove a directory (delete)

Question 17

control-c

Answer 17

hold buttons to get out of an infinite loop

Question 18

RubyGems or “gems”

Answer 18

There are two main sides to this term. The first side refers to a collection of Ruby files, or Ruby library, that performs a certain task. The other side refers to the publishing system that is behind organizing, listing, and publishing those libraries, or gems.

gem install

Question 19

pry

Answer 19

used for dubugging Ruby code. must add it to code.

Used similar to irb.

# preparation.rb
require "pry"

a = [1, 2, 3]
a &laquo_space;4
binding.pry # execution will pause here, allowing you to inspect all objects
puts a

Question 20

irb

Answer 20

a built in interactive environment. runs ruby code in the terminal.

Question 21

string

Answer 21

A string is a list of characters in a specific sequence. Strings are surrounded by either single quotes (‘hi there’) or double quotes (“hi there”).

# Ex. 1: with double quotes
"The man said, 'Hi there!'"

# Ex 2: with single quotes and escaping
'The man said, \'Hi there!\''

Question 22

string interpolation

Answer 22

irb :001 > a = ‘ten’
=> “ten”

irb :002 > “My favorite number is #{a}!”
=> “My favorite number is ten!”

Question 23

symbols

Answer 23

created by placing a colon (:) before a word

a symbol is used when you want to reference something like a string but don’t ever intend to print it to the screen or change it.

Examples of symbols
:name
:a_symbol
:“surprisingly, this is also a symbol”

Question 24

Numbers

Answer 24

The most basic form of a number is called an integer. It is represented by the whole number only, with no decimal point. A more complex form of a number is called a float. A float is a number that contains a decimal.

# Example of integers
1, 2, 3, 50, 10, 4345098098

# Example of floats
1.2345, 2345.4267, 98.2234

Question 25

nil

Answer 25

In programming, we need a way to express “nothing”, and in Ruby, we do this through something called nil. A variable with a value of nil could be described as having ‘nothing’ or being ‘completely empty’, or even just simply ‘not any specific type’.

It is possible to check if something is a nil type by using .nil?

irb :001 > “Hello, World”.nil?
=> false

Question 26

modulo

Answer 26

% symbol

gives the remainder of a division operation

Question 27

== operator

Answer 27

This compares the object on the left of the == with the object on the right and returns either true or false.

Question 28

+ operator

Answer 28

String concatenation to join two strings together.

irb :001 > ‘foo’ + ‘foo’
=> “foofoo”

irb :002 > ‘foo’ + ‘bar’
=> “foobar”

Question 29

to_i

Answer 29

will convert a String to a Fixnum

irb :001 > ‘12’.to_i
=> 12

Question 30

to_f

Answer 30

will convert a String to a float

irb :005 > ‘4’.to_f
=> 4.0

Question 31

to_s

Answer 31

convert an integer or float to a string

Question 32

array

Answer 32

An array is used to organize information into an ordered list. The list can be made up of strings, integers, floats, booleans, or any other data type. In Ruby, an array is denoted by square brackets [ ]. Inside the brackets you can create a list of elements separated by commas.

irb :001 > [1, 2, 3, 4, 5]
=> [1, 2, 3, 4, 5]

Question 33

index

Answer 33

Each element in an array can be accessed via an index. The indexes are numbered starting at zero.

Question 34

hash

Answer 34

A hash, sometimes referred to as a dictionary, is a set of key-value pairs. It is represented with curly braces { }. A key-value pair is an association where a key is assigned a specific value. A hash consists of a key, usually represented by a symbol, that points to a value (denoted using a =>) of any type of data.

irb :001 > {:dog => ‘barks’}
=> {:dog => ‘barks’}

Question 35

expression

Answer 35

An expression is anything that can be evaluated, and pretty much everything you write in Ruby is an expression. An expression in Ruby always returns something, even if that’s an error message or nil.

Question 36

puts

Answer 36

we’re telling Ruby to print something to the screen. However, puts does not return what is printed to the screen.

Expressions do something, but they also return something. The value returned is not necessarily the action that was performed.

irb :001 > puts ‘stuff’
stuff
=> nil

So you can see that the word stuff was printed to the console and then a nil, which is Ruby’s way of saying ‘nothing’, was returned. It’s important to understand that distinction.