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#!/usr/bin/env python
# -*- coding: utf-8 -*-
class Worker(object):
def work(self):
print "I'm working!!"
class Manager(object):
def __init__(self):
self.worker = None
def set_worker(self, worker):
assert isinstance(worker, Worker), '`worker` must be of type {}'.format(Worker)
self.worker = worker
def manage(self):
if self.worker is not None:
self.worker.work()
# And some complex codes go here....
class SuperWorker(object):
def work(self):
print "I work very hard!!!"
# OK... now you can see what happend if we want the `Manager` to support `SuperWorker`.
# 1. The `set_worker` must be modified or it will not pass the type-checking.
# 2. The `manage` method should be re-test, which means you may or may not have to
# rewrite the testing code.
def main():
worker = Worker()
manager = Manager()
manager.set_worker(worker)
manager.manage()
# The following will not work...
super_worker = SuperWorker()
try:
manager.set_worker(super_worker)
except AssertionError:
print "manager fails to support super_worker...."
if __name__ == "__main__":
main()