适配器模式

在计算机编程中，适配器模式（有时候也称包装样式或者包装）将一个类的接口适配成用户所期待的。一个适配允许通常因为接口不兼容而不能在一起工作的类工作在一起，做法是将类自己的接口包裹在一个已存在的类中。

def running_competition(*list_of_animals):
    if len(list_of_animals)<1:
        print("No one Running")
        return
    fastest_animal = list_of_animals[0]
    maxspeed = fastest_animal.running_speed()
    for animal in list_of_animals[1:]:
        runspeed =  animal.running_speed()
        if runspeed > maxspeed:
            fastest_animal = animal
            maxspeed = runspeed
    print("winner is {0} with {1} Km/h".format(fastest_animal.name,maxspeed))


class Cat(object):
    def __init__(self, name, legs):
        self.name = name
        self.legs = legs

    def running_speed(self,):
        if self.legs>4 :
            return 20
        else:
            return 40

running_competition(Cat('cat_a',4),Cat('cat_b',3))


class Fish(object):
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def swim_speed(self):
        if self.age < 2:
            return 40
        else:
            return 60

# to let our fish to participate in tournament it should have similar interface as
# cat, we can also do this by using an adaptor class RunningFish
class RunningFish(object):
    def __init__(self, fish):
        self.legs = 4 # dummy
        self.fish = fish

    def running_speed(self):
        return self.fish.swim_speed()
        
    def __getattr__(self, attr):
        return getattr(self.fish,attr)

running_competition(Cat('cat_a',4),
                    Cat('cat_b',3),
                    RunningFish(Fish('nemo',3)),
                    RunningFish(Fish('dollar',1)))

上面的例子中，Fish的并不具有running_speed()方法，所以添加适配器类RunningFish，输出结果为：

winner is cat_a with 40 Km/h
winner is nemo with 60 Km/h