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Example of using Observable in Ruby
require 'observer'
class CoffeeShop
include Observable
attr_reader :customers
def initialize(name, capacity)
@name = name
@capacity = capacity
@customers = []
end
def enter(customer)
unless full?
changed
@customers.push(customer)
notify_observers(Time.now)
end
end
def depart(customer)
unless empty?
changed
@customers.delete(customer)
notify_observers(Time.now)
end
end
def full?
@customers.count >= @capacity
end
def empty?
@customers.count.zero?
end
end
class CoffeeShopObserver
def initialize(shop)
@shop = shop
@shop.add_observer(self)
end
end
class CoffeeShopEmptyObserver < CoffeeShopObserver
def update(time)
if @shop.empty?
puts "#{time}: The shop is EMPTY so some staff can go home."
end
end
end
class CoffeeShopFullObserver < CoffeeShopObserver
def update(time)
if @shop.full?
puts "#{time}: The shop is FULL - quick call more staff!"
end
end
end
coffee_shop = CoffeeShop.new("Costa", 3)
CoffeeShopEmptyObserver.new(coffee_shop)
CoffeeShopFullObserver.new(coffee_shop)
potential_customers = %w(Bob Harry William Darren Brian Susan Kelly John Kevin)
customer_actions = [:enter, :enter, :depart] #enter in twice to try and encourage more customers!
20.times do
action = customer_actions.sample
if action == :enter
customer = potential_customers.sample
potential_customers.delete(customer)
puts "Entering: #{customer}"
coffee_shop.enter(customer)
else
unless coffee_shop.empty?
customer = coffee_shop.customers.sample
puts "Leaving #{customer}"
potential_customers.push(customer)
coffee_shop.depart(customer)
end
end
sleep 0.1
end
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