Ruby Cheatsheet

cheetsheet.rb

#string
str = "str #{placeholder}"
str.length
str = str + "concatenate"
"albert".gsub("al", "ro") #replace
str[3]

#array
arr = ["alb", "ert", 25]
arr.size
arr << "lin"
arr.delete_at(2)
arr.each do { something }

#hash
hash = { al: "bert", yingkui: "lin"}
hash.al
hash.delete(:a)

#Ruby Bits 1
unless = if !
puts "albert" unless old?
nil == false #only these two
albert ||= "" # albert = "" unless albert
# every condition returns a value
albert || "Not found"
if object_a == object_b
self.method
private
def method
arr.from
arr.to

# module extended or included by class
include GameUtils # include instance methods
game.extend(Playable)
extend GameUtils # include class methods

def self.included(base)
  base.extend(ClassMethods)
end

extend ActiveSupport::Concern

included do
  load_game_list
end



#Ruby BIts 2
#Struct
Game = Struct.new(:name, :year, :system) do 
  def to_s
    "#{name}#{year}"
  end
end

#alias_method
alias_method :find_all, :all

#define_method
SYSTEMS = ['SNES', 'PS1', 'Genesis']
  
SYSTEMS.each do |system|
  define_method "runs_on_#{system.downcase}?" do
    self.system == system
  end
end

#send method
library.send(:list)
library.send(:emulate, "Contra")
library.method(:list).call
library.method(:emulate).call("Contra")

# combine
[:each, :map, :select].each do |method|
  define_method method do |&block|
    games.send(method, &block)
  end
end

rails.sh

$rails new project_name
$rails server
$rails g scaffold name attribute:type
$rake db:migrate
$bundle install
$bundle check

symbols

# class instance / methods
before_save :set_password

foreign_key: :product_id