Python的组合模式与责任链模式编程示例

class Trunk(object):
 '''树干'''
 def __str__(self):
 pass
 
 def subtree(self):
 pass
 
class Composite(Trunk):
 def __init__(self, left=None, right=None, length=None):
 self.left=left
 self.right=right
 self.length=length
 
 def __str__(self):
 # 这个结果是在调用subtree()的时候返回
 if self.length:
 return "(" + self.left.__str__() + ", " + self.right.__str__() + ")" + ": " + str(self.length)
 else:
 return "(" + self.left.__str__() + ", " + self.right.__str__() + ")"
 
 # 这里其实就是一个技巧，通过这个函数返回下一级的对象，也就是它既是对象还可以是对象的容器
 def subtree(self): 
 return Composite(self.left, self.right)
 
class Leaf(Trunk):
 '''叶子类，它没办法继续延伸了'''
 def __init__(self, name, length=None):
 self.name = name
 self.length=length
 self.left = None
 self.right = None
 
 def __str__(self):
 return self.name + ": " + str(self.length)
 
 def subtree(self):
 return Leaf(self.name, self.length)
 
 
if __name__ == "__main__":
 # 只有叶子那么就直接返回__str__的拼装结果
 t1 = Leaf('A', 0.71399)
 print t1
 # 有个2个叶子的组合，返回的是2个叶子的对象的组合
 t2 = Composite(Leaf('B', -0.00804),
 Leaf('C', 0.07470))
 print t2
 # 这个是嵌套的叶子的组合，树干上面有树枝，树枝上面有叶子
 t3 = Composite(Leaf('A', 0.71399),
 Composite(Leaf('B', -0.00804),
 Leaf('C', 0.07470), 0.1533), 0.0666)
 
 print t3
 # 直接通过左右节点找到对应的叶子对象了
 t4 = t3.right.right.subtree()
 print t4
 # t3的左树其实就是叶子对象了
 t5 = t3.left.subtree()
 print t5

class BaseHandler:
 # 它起到了链的作用
 def successor(self, successor):
 self.successor = successor
 
class ScoreHandler1(BaseHandler):
 def handle(self, request):
 if request > 90 and request <= 100:
 return "A+"
 else:
 # 否则传给下一个链，下同，但是我是要return回结果的
 return self.successor.handle(request)
 
class ScoreHandler2(BaseHandler):
 def handle(self, request):
 if request > 80 and request <= 90:
 return "A"
 else:
 return self.successor.handle(request)
 
class ScoreHandler3(BaseHandler):
 def handle(self, request):
 if request > 70 and request <= 80:
 return "B+"
 else:
 return "unsatisfactory result"
 
class Client:
 def __init__(self):
 h1 = ScoreHandler1()
 h2 = ScoreHandler2()
 h3 = ScoreHandler3()
 # 注意这个顺序，h3包含一个类似于default结果的东西，是要放在最后的，其他的顺序是无所谓的，比如h1和h2
 h1.successor(h2)
 h2.successor(h3)
 
 requests = {'zhangsan': 78,
 'lisi': 98,
 'wangwu': 82,
 'zhaoliu': 60}
 for name, score in requests.iteritems():
 print '{} is {}'.format(name, h1.handle(score))
 
if __name__== "__main__":
 client = Client()