strategy-pattern.coffee

# Greeter is a class of object that can greet people.
# It can learn different ways of greeting people through
# 'Strategies.'
#
# This is the Greeter constructor.
Greeter = (strategy) ->
  @strategy = strategy

# Greeter provides a greet function that is going to
# greet people using the Strategy passed to the constructor.
Greeter::greet = ->
  @strategy()

# Since a function encapsulates an algorithm, it makes a perfect
# candidate for a Strategy.
#
# Here are a couple of Strategies to use with our Greeter.
politeGreetingStrategy = ->
  console.log 'Hello.'

friendlyGreetingStrategy = ->
  console.log 'Hey!'

boredGreetingStrategy = ->
  console.log 'sup.'

# Let's use these strategies!
politeGreeter = new Greeter(politeGreetingStrategy)
friendlyGreeter = new Greeter(friendlyGreetingStrategy)
boredGreeter = new Greeter(boredGreetingStrategy)

politeGreeter.greet() #=> Hello.
friendlyGreeter.greet() #=> Hey!
boredGreeter.greet() #=> sup.