Cheat Sheet Ruby

array = %w(hello world) # => ["hello", "world"]

"%.2f" % 10    # => "10.00"
 "%.2f €" % 10 # => "10.00 €"

a, b = [1, 2] , 3
eval("a << b") # => [1, 2, 3]

string = <<-STRING
Hello John
How are you today ?
Goodbye
STRING
# => "Hello John\nHow are you today ?\nGoodbye\n"

case year
  when 1970..1979: "disco"
  when 1980..1989: "eighties"
  when 1990..1999: "dance"
  else "RnB"
end

object.send(:my_method)

define_method(:my_method) do |foo, bar| # or even |*args|
  # do something
end
# est équivalent
def my_method(foo, bar)
  # do something
end
['draft','waiting','paid'].each do |status|
  define_method("#{status}?") { self.status == status }
end

String.instance_methods # => [:encode, :encode!, :include?, :%, :*, :+, :count, ...]
String.instance_methods(false) # sans les méthodes héritées
String.instance_methods(false).grep(/what/) # => [:count]

stringify = proc { |object| object.to_s }
(1..10).map(&stringify) # => ["1", "2", "3", "4", "5", "6", "7", "8", "9", "10"]

[1, 2, 3].map { _1 + 3 }
=> [4, 5, 6]

User.new.method(:confirmed?).source.display
User.instance_method(:confirmed?).source.display

# will print

def confirmed?
  !!confirmed_at
end

User.new.method(:active?).source_location
# ["/Users/alexandrebouvier/my_app/app/models/user.rb", 63]

def greet(hash = {})
  case hash
  in {greeting: greeting, first_name: first_name, last_name: last_name}
    greet(greeting: greeting, name: "#{first_name} #{last_name}")
  in {greeting: greeting, name: name}
    puts "#{greeting}, #{name}"
  in {name: name}
    greet(greeting: "Hello", name: name)
  in {greeting: greeting}
    greet(greeting: greeting, name: "Anonymous")
  else
    greet(greeting: "Hello", name: "Anonymous")
  end
end

greet # Hello, Anonymous
greet(name: "John") # Hello, John
greet(first_name: "John", last_name: "Doe") # Hello, John Doe
greet(greeting: "Bonjour", first_name: "John", last_name: "Doe") # Bonjour, John Doe
greet(greeting: "Bonjour") # Bonjour, Anonymous

def method_missing; end

begin
  # someting that may fail
rescue
  # someting to execute in case of failure
else
  # someting to execute in case of success
ensure
  # something that will always execute
end