class Duck(object):
# 上面使用继承，这里通用的使用参数方式，传入的就是操作工厂的类
def __init__(self, strategy=None):
self.action = None
self.count = 0
if strategy:
# 指定策略，那么执行action就是用这个类的实例
self.action = strategy()
def fly(self, kind):
if self.action:
self.count += 1
# 这里的第二个参数self，算是炫技吧，就是为了让操作的方法获得这里计算好的count
return self.action.fly(kind, self)
else:
raise UnboundLocalError('Exception raised, no strategyClass supplied to Duck!')
# 注意这里没有继承Duck，因为是以参数的方式传入类名
class Duck1(object):
def fly(self, kind, instance):
return 'Duck1 fly kind: ' + kind + '#' + str(instance.count)
class Duck2(object):
def fly(self, kind, instance):
return 'Duck2 fly kind: ' + kind + '#' + str(instance.count)
if __name__ == '__main__':
duckfly = Duck()
duck1fly = Duck(strategy=Duck1)
duck2fly = Duck(strategy=Duck2)
try:
print duckfly.fly('yes')
except Exception as e:
print "The following exception was expected:"
print e
print duck1fly.fly('yes')
print duck1fly.fly('no')
print duck1fly.fly('yes')
print duck2fly.fly('yes')
print duck2fly.fly('no')
