Sihui

# Returning a proc from a method
def fancy_proc_maker
  proc { puts 'Call me fancy' }
end

fancy_proc = fancy_proc_maker
fancy_proc.call
  
# The above code will print:
# Called me fancy

Sihui

Proc.new { puts 'I am a proc' }
proc { puts 'I am a proc' }
  
lambda { puts 'I am a lambda' }
-> { puts 'I am a lambda' }

Sihui

#Lambda
# 1. lambda followed by a code block
lambda { puts 'Hi' }
lambda do
  puts 'Hi'
end
#2. -> (stabby lambda)
-> { puts 'Hi' }
-> do
  puts 'Hi'

Sihui

#Proc
#1. Proc.new followed by a code block
Proc.new { puts 'Hi' }
Proc.new do
  puts 'Hi'
end
#2. proc followed by a code block
proc { puts 'Hi' }
proc do
  puts 'Hi'

Sihui

#Code Block
#1 {} Mostly used as a one-liner
{ puts 'Hi' }
#2. do end
do 
  puts 'Hi'
end
#arguments are 
#  wrapped between ||
[1, 2].map {|num| num * 2}

Sihui

# Only -> 
#  takes argument outside of {}
->(arg) { puts arg }
# The rest 
#  takes argument in between ||
{ |arg| puts arg }
proc do |arg|
  puts arg
end
lambda { |arg| puts arg }

Sihui

class GoToOrderSihui
  def vessel
    Bowl
  end
  
  def meat
    Steak
  end
  
  def toppings

Sihui

class DietOrder
  def vessel
    raise 'What is your choice?'
  end
  
  def meat
    raise 'What is your choice?'
  end
  
  def toppings

Sihui

class DietOrderSihui
  def vessel
    Bowl
  end
  
  def meat
    Steak
  end
  
  def toppings

Sihui

class BenDietOrder < DietOrder
  def vessel
    Tacos
  end
  
  def meat
    Carnitas
  end
end