python设计模式：链式建造者模式

class Pizza:
	def __init__(self, builder):
		self.garlic = builder.garlic
		self.extra_cheese = builder.extra_cheese
		
	def __str__(self):
		garlic = 'yes' if self.garlic else 'no'
		cheese = 'yes' if self.extra_cheese else 'no'
		info = ('Garlic: {}'.format(garlic), 'Extra cheese: {}'.format(cheese))
		return '\n'.join(info)
		
	class PizzaBuilder:
		def __init__(self):
			self.extra_cheese = False
			self.garlic = False
	
		def add_garlic(self):
			self.garlic = True
			return self
			
		def add_extra_cheese(self):
			self.extra_cheese = True
			return self
			
		def build(self):
			return Pizza(self)
			
if __name__ == '__main__':
	pizza = Pizza.PizzaBuilder().add_garlic().add_extra_cheese().build()
	print(pizza)