ruby workshop

gistfile1.rb

# welcome to Ruby. i'm a comment.

# > irb
# `irb` is the command line ruby console. it opens up a REPL - an interactive terminal that you can evaluate ruby statements in. similar to python's `python`.

# in Cloud9, choose "Runner: Shell command" from the dropdown at the bototm (near CWD). Then run "irb" as your command.

1 + 1
# => 2

"hello world"
# => "hello world" 

"hello world".class
# => String 

"hello world".upcase
# => "HELLO WORLD" 
"hello world".upcase()
# => "HELLO WORLD" 

"everything is a method".reverse
# => "dohtem a si gnihtyreve"

"everything is an object".object_id
# => 18937180 

"hello world".gsub("hello", "goodbye, cruel")                                                                                                                                                             
# => "goodbye, cruel world" 

variable = "boo"
"boo" == "urns"
# => false

array = []
array << 1
array << 2
array
# > [1, 2]

array << "technically objects of any type can go into an array, but that's usually a pretty bad idea"
# => [1, 2, "technically objects of any type can go into an array, but that's usually a pretty bad idea"]

array.pop
# => "technically objects of any type can go into an array, but that's usually a pretty bad idea"

array
# > [1, 2]

array.nil?
# => false

array.empty?
# => false

[].empty?
# => true

nil.nil?
# => true

nil.empty?
# NoMethodError: undefined method `empty?' for nil:NilClass

hash = {}
hash[:brown] = 'tasty'

hash
# => {:brown=>"tasty"}

hash[:brown]
# => 'tasty'

hash['string key'] = 'you can use different types as keys'
hash['string key']
# => 'you can use different types as keys'
# but it's usually a bad idea. you should use symbols unless you have a good reason. symbols start with colons, like in the example just below.

first_hash = {omg: "wow", key: "value", convoluted: "example"}
second_hash = {:omg => "wow", :key => "value", :convoluted => "example"}
first_hash == second_hash
# => true
# two ways to write the same thing - you'll see both, but should use the first whenever you can

hackers = ['alex', 'dave', 'jun', 'adam', 'nick']
hackers.each do |name|
  puts(name) # print each name out one by one
end
hackers.reverse.each_with_index do |name, index|
  puts "Hacker ##{index + 1}: #{name}" # tanda competence ranking
end
# you always use .each to iterate over things. it's the equivalent of `for` in other langauges. `for` also exists in ruby but is slightly different and internally implemented as .each

hackers.map {|h| h.upcase.reverse}
# => ["XELA", "EVAD", "NUJ", "MADA", "KCIN"]
hackers
# => ["alex", "dave", "jun", "adam", "nick"]

hackers.map! {|h| h.upcase.reverse}
# => ["XELA", "EVAD", "NUJ", "MADA", "KCIN"]
hackers
# => ["XELA", "EVAD", "NUJ", "MADA", "KCIN"]

# "bang" methods (methods with exclamation marks) are generally methods that are "destructive" - they modify the object they are being called on, rather than returning a new, different one
# eg. Array.map!, String.chomp!, many many more

hash_that_you_can_iterate_over = {omg: "wow", key: "value", convoluted: "example"}
hash_that_you_can_iterate_over.each do |key, value|
  puts(key) # :omg
  puts(value) # "wow"
end

class Animal
  attr_accessor :name # define getters and setters

  def initialize(name)
    @name = name # set instance variable
  end

  def human?
    false # implicit return
  end

  def talk!
    raise NotImplementedError.new # "throw an exception"
  end
end

class Cat < Animal
  def talk!
    puts "meow" # prints to stdout
  end
end

cat = Cat.new("Dave")
cat.human? # false
cat.talk! # "meow"

puts "i am printing something to standard output (it'll probably show up on your screen, but it could also write to a logfile if you configure that)"
puts "" # line break

puts "what is your name?"
name = gets # read from standard input. this would prompt the user of the program to type something in to the command line.
name
# => "....\n"
name.chomp!
name
# => "...."

puts "what is your quest?"
quest = gets.chomp # http://ruby-doc.org/core-2.2.0/String.html#method-i-chomp

puts "what is the airspeed velocity of an unladen swallow?"
velocity_answer = gets.chomp

correct_answer = velocity_answer == "european or american?"
puts "you are #{correct_answer ? "correct" : "incorrect"}!"

text = "Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum."
File.open("filename.txt", "wb") {|f| f.write(text)}
# File.open gives you a "block". This is like a callback in some functional languages.
# Basicaly the code inside the block (between the { and }) gets run at a specfied later time - in this case, when the file has been opened for writing.

text_read_from_file = File.read("filename.txt")
# => "Lorem Ipsum..."

`open https://gist.github.com/ghiculescu/97fbfe97c5abd77dd359`