01_recap.rb

# string
"Hello world"

# integer
423

# float
3.14

# array
[ "micheal", "francis" ]

# range
(1..10)

# booleans
true
false && true || false


# Hash
my_hash = {}
p my_hash

02_array_crud.rb

students =     ['Peter', 'Mary', 'George', 'Emma']
student_ages = [24,     25,       22,       20   ]
# indexes         0.       1.       2.         3
students.each_with_index do |student, index|
  puts "#{student} is #{student_ages[index]} years old"
end

# CRUD ARRAY
# C array = [ "Peter", "Mary", "George", "Emma" ]
# R array[0]
# U array[0] = new_value
# D array.delete_at(index)

03_hash_crud.rb

# CRUD HASH
# Create
ages = {
  'Peter' => 24,
  'Mary' => 25,
  'George' => 22
}
# Hash.new

# p ages

# Read
ages["Peter"]
# p "Peter is #{ages["Peter"]}"

# Update a value
ages['Peter'] += 1
# p ages['Peter']

# Add a new Key Value pair
ages['Seb'] = 18
# p ages['Seb']

# Delete
ages.delete('Peter')
ages['Ringo'] = 100
# p ages

04_city.rb

paris = {
  'country' => 'France',
  'population' => 2211000
}

# p paris['country']
# p paris['population']

# paris['monument'] = 'Tour de Eiffel'

# p paris['monument']

# paris['population'] += 9000
# p paris['population']

# paris.each do |key, value|
#   puts "#{value}"
#   puts "Paris' #{key} is #{value}"
# end

05_hash_methods.rb

paris = {
  'country' => 'France',
  'population' => 2211000
}

p paris.key?('country')
#=> true
p paris.key?('monument')
#=> false
p paris.value?(2211100)
#=> true
p paris.value?(123123123123)
#=> false

# to get all the values:
p paris.values
# to get all the keys:
p paris.keys

p paris.size
#=> 2

06_symbols.rb

# basic symbol
p :hello

# Transform to a symbol
p "goodbye".to_sym

:hello == "hello"
#=> false

07_hash_syntax.rb

# 1) With Stings as identifiers
paris = {
  "country" => "France",
  "population" => 2211000
}

# 2) With Symbols as identifiers (maintaining the arrow)
paris = {
  :country => 'France',
  :population => 2211000
}

# 3) Modern Syntax with Symbols
paris = {
  country: 'France',
  population: 2211000
}

p paris[:county] # for 2 and 3
p paris["country"] # for 1

08_last_method_argument.rb

# the last argument in a method can be accepted as a hash!
def tag(name, content, attrs = {})
  tag_attrs = attrs.map { |k, v| "#{k}='#{v}'" }.join(' ')
  return "<#{name} #{tag_attrs}>#{content}</#{name}>"
end

# we can even drop the curly braces! (notice the key value pairs after 'Hello World')
tag('h1', 'Hello world', class: 'italics', id: 'batch-423')

09_read_csv.rb

require 'csv'
# similar to the Date object we need to
# import this to help us out!

CSV.foreach('cities.csv') do |row|
  # each row is an array
  # p row
  # a nice 'puts' to print out our data
  puts "#{row[0]} has a population of #{row[1]}, its monument is #{row[2]}"
end

10_cities.csv

11_cities.json

{
  "name": "Paris",
  "population": 2211000
}

12_github.rb

require 'open-uri' # require to open links (urls)
require 'json' # require this to parse/extract JSON

# ask our user for his githubname
puts "What is your githubname?"
githubname = gets.chomp

# the link to the API
url = "https://api.github.com/users/#{githubname}"

# open the link and read it
user_info = open(url).read
# parse the information
json = JSON.parse(user_info)

# display a nice sentence to the user, with the info
puts "#{json["name"]} works at #{json["company"]}"

B423_00_index.txt

Hashes and Symbols