GoF design pattern - Chain of Responsibility

chain_of_responsibility.py

# -*- coding: utf-8 -*-


class Handler:
	def successor(self, successor):
		self.successor = successor


class ConcreteHandler1(Handler):
	def handle(self, request):
		if 0 < request <= 10:
			print('request {} handled in handler 1'.format(request))
		else:
			self.successor.handle(request)


class ConcreteHandler2(Handler):
	def handle(self, request):
		if 10 < request <= 20:
			print('request {} handled in handler 2'.format(request))
		else:
			self.successor.handle(request)


class ConcreteHandler3(Handler):
	def handle(self, request):
		if 20 < request <= 30:
			print('request {} handled in handler 3'.format(request))
		else:
			print('end of chain, no handler for {}'.format(request))


class Client:
	def __init__(self):
		h1 = ConcreteHandler1()
		h2 = ConcreteHandler2()
		h3 = ConcreteHandler3()

		h1.successor(h2)
		h2.successor(h3)

		self.handlers = (h1, h2, h3)

	def delegate(self, requests):
		for request in requests:
			self.handlers[0].handle(request)


if __name__ == '__main__':
	client = Client()
	request = [2, 5, 14, 22, 18, 3, 35, 27, 20]
	client.delegate(request)