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#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Here we solve the issues in the design in `python_code.bad.DIP` with an interface
# (implemented with abstract class).
from abc import ABCMeta, abstractmethod
class IWorker(object):
__metaclass__ = ABCMeta
@abstractmethod
def work(self):
pass
# `IWorker` defines a interface which requires `work` method.
class Worker(IWorker):
def work(self):
print "I'm working!!"
class Manager(object):
def __init__(self):
self.worker = None
def set_worker(self, worker):
assert isinstance(worker, IWorker), '`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(IWorker):
def work(self):
print "I work very hard!!!"
# Now, the manager support `SuperWorker`...
# In addition, it will support any worker which obeys the interface defined by `IWorker`!
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)
manager.manage()
except AssertionError:
print "manager fails to support super_worker...."
if __name__ == "__main__":
main()