Good documentation
and
lot of good articles

• Ruby Doc
• Codecademy
• Code School

Frameworks & Tools

Underscore in numbers

# bad - how many 0s are there?
num = 1000000


# good - much easier to parse for the human brain
num = 1_000_000

String Interpolation

 # concatenation ;(
"My name is " + user.name + " and I have " + user.age + " years old."


# interpolation :)
"My name is #{user.name} and I have #{user.age} years old."


# even it works
"You will have #{user.age + 1} years old next year."

Access modifiers

class User

  def yell_hello
    puts "hello"
  end
  
  protected
  def say_hello
    puts "hello"
  end
  
  private
  def whisper_hello
    puts "hello"
  end
end

Symbol

# It's just a name and an internal ID
:open
:closed

puts "hello".object_id
puts "hello".object_id
puts :hello.object_id
puts :hello.object_id

# 70347643412820
# 70347646952580
# 923848
# 923848

Double Pipes or Equals

a = nil
b = 20
c = 30
a ||= b    
puts a          #=> 20

a ||= c    
puts a          #=> 20


# daily usage
class User
  define initialize(name)
    @name ||= name
  end
end

Question Marks

"hello".empty?   #=> false
" ".empty?       #=> false
"".empty?        #=> true

"hello".delete "l"  #=> heo
"hello".delete "x"  #=> hello
"hello".delete! "x" #=> nil 
    

Dynamic Typing

(Duck Typing)

# define the type in runtime
x = 100
puts x.class 

# type is dinamically changed
x = "hello"
puts x.class

# String
# Fixnum

n = "10"

# yeap
puts n + " days"

# nope
puts n + 1

Blocks

# Monkeypatching
class Array
  def double!
    self.each_with_index do |n, i|
      self[i] = yield(n)
    end
  end
end

array = [1, 2, 3, 4]

array.double! do |n| 
  n * 2
end

puts array.inspect  #=>[2, 4, 6, 8]

Metaprogramming

my_object = Object.new

# define a set method
def my_object.set_my_variable=(var)
  @my_instance_variable = var
end

# define a get method
def my_object.get_my_variable
  @my_instance_variable
end

my_object.set_my_variable = "Hello"
my_object.get_my_variable # => Hello

Metaprogramming

class Module
  def attribute(*attribs)
    attribs.each do |a|
      define_method(a) { instance_variable_get("@#{a}") }
      define_method("#{a}=") { |val| instance_variable_set("@#{a}", val)}
    end
  end
end

class Person
  attribute :name, :email
end

person = Person.new
person.name = "Max"
p person.name

Hash

status = { "open" => "Open", "close" => "Close" }
    
status = { :open => "Open", :close => "Close" }

status = { open: "Open", close: "Close" }

status = { 0 => "Open", 1 => "Close" }

# used a lot
Person.create(name: "John Doe", age: 27)

def self.create(params)
  @name = params[:name]
  @age  = params[:age]
end

Iterators

# times
100.times do
  puts "\o/"
end

# each
users.each do |user|
  puts user.name
end


# each_with_index
users.each_with_index do |user, index| 
  puts "#{index} - #{user.name}"
end

Enumerators

# all?
%w[ant bear cat].all? { |word| word.length >= 3 } #=> true

# any?
%w[ant bear cat].any? { |word| word.length >= 3 } #=> true

# none?
%w{ant bear cat}.none? { |word| word.length == 5 } #=> true

# map
(1..4).map { |i| i*i }      #=> [1, 4, 9, 16]

# collect
(1..4).collect { "cat"  }   #=> ["cat", "cat", "cat", "cat"]

# find_all
(1..10).find_all { |i|  i % 3 == 0 }   #=> [3, 6, 9]

# select
[1,2,3,4,5].select { |num|  num.even?  }   #=> [2, 4]

# group_by
(1..6).group_by { |i| i%3 }   #=> {0=>[3, 6], 1=>[1, 4], 2=>[2, 5]}

# reject
(1..10).reject { |i|  i % 3 == 0 }   #=> [1, 2, 4, 5, 7, 8, 10]

# sort
%w(rhea kea flea).sort          #=> ["flea", "kea", "rhea"]

Unless statement

# negative if ;(
if !is_true
  do_something
end

# unless :)
unless is_true
  do_something
end

Single lines

# if
do_something if some_condition

# until
do_something until some_condition

# while
do_something while some_condition

# blocks
names.select { |name| name.start_with?('S') }.map { |name| name.upcase }