共享类变量

Question

这是我的意思的一个非常简短的例子。

class class1():
    def method1(self):
        self.variable1 = 5
class class2():
    def method2(self):
        self.variable2 = var1.variable1 * 2
class class3():
    def __init__(self):
        self.var1 = class1()
        self.var2 = class2()

instance = class3()
instance.var1.variable1 = 10
instance.var2.method2()
print instance.var2.variable2

上面的代码显然会停在倒数第二行，因为 class2 不知道 var1 是什么。

现在我知道这样的事情对于子类是可行的，或者只是通过将所有方法都放在同一个类下。但就我而言，我不认为（我不是说我知道，因为我不是很有经验，但我不认为）这是一个可行的解决方案。

这是一个bigger sample code（我实际使用的），这还不是全部，还有两个其他（甚至更大的）系统比我需要实施（技能和津贴）。因此，如果我要依赖子类，我会在一个庞大的类中加载子类，而不是稍后在代码中组合许多类。

有什么好的方法可以解决这个问题？我只是做错了吗？

编辑/更新：另请注意，此代码将被多次重复用于许多不同的变量，而不仅仅是一个（当然。）

Answer 1

可能是这样的：

class NotEnoughMagic(Exception):
    pass


class Character(object):
    fire = 0
    magic = 0
    hp = 100
    armor = 1
    def take_damage(self, amount):
        self.hp -= amount
        if self.hp <= 0:
            print '%s HAS DIED!' % type(self).__name__
    def walk(self):
        pass
    def attack(self, target, attack_points):
        target.take_damage(attack_points / target.armor)


class Monster(Character):
    fire = 50
    hp = 150
    armor = 2
    def punch(self, target):
        self.attack(target, 25)


class Magician(Character):
    magic = 10
    def magic_armor(self):
        self.hp += 20
        self.magic -= 10
    def sword_attack(self, target):
        self.attack(target, 20)
    def magic_attack(self, target):
        """Does tons of damage but uses all magic"""
        if self.magic > 0:
            self.attack(target, 100)
            self.magic = 0
        else:
            raise NotEnoughMagic()

用法：

>>> monster     = Monster()
>>> magician = Magician()
>>> 
>>> print magician.hp
100
>>> print monster.hp
150
>>> 
>>> monster.punch(magician)
>>> magician.sword_attack(monster)
>>> 
>>> print magician.hp
75
>>> print monster.hp
140
>>> 
>>> monster.punch(magician)
>>> magician.magic_attack(monster)
>>> 
>>> print magician.hp
50
>>> print monster.hp
90
>>> 
>>> monster.punch(magician)
>>> magician.magic_attack(monster)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 14, in magic_attack
__main__.NotEnoughMagic
>>> 
>>> print magician.hp
25
>>> print monster.hp
90
>>> 
>>> monster.punch(magician)
Magician HAS DIED!
>>> magician.sword_attack(monster)
>>> 
>>> print magician.hp
0
>>> print monster.hp
80

一些潜在的游戏逻辑：

>>> # Gang of monsters
... monsters = [Monster() for x in range(10)]
>>> magician = Magician()
>>> 
>>> # Prepare for battle
... while magician.magic > 0:
...     magician.magic_armor()
...     
... # Put on some chain mail
... magician.armor += 5
  File "<stdin>", line 6
    magician.armor += 5
           ^
SyntaxError: invalid syntax
>>> 
>>> 
>>> while magician.hp > 0:
...     for m in monsters:
...             m.punch(magician)
... 
Magician HAS DIED!
Magician HAS DIED!
Magician HAS DIED!
Magician HAS DIED!
Magician HAS DIED!
Magician HAS DIED!
Magician HAS DIED!
>>> 

---

更新：

另外，需要注意的一件事是mixins。例如，如果您想向广泛的类集添加额外的功能，而不是整个继承树。

class TeleportAbilityMixin(object):
    def teleport(self, destination):
        cost = 20
        if self.mp >= cost:
            # Unpack the x, y coordinates
            self.x, self.y = destination
            self.mp -= cost

class TeleportingMagician(Magician, TeleportAbilityMixin):
    pass

m = TeleportingMagician()
new_location = (10, 5)
m.teleport(new_location)