将自变量作为参数传递给mixin父方法的正确方法

Question

我必须模拟一个战士和他可以执行的不同类型的攻击。其思想是使用mixin来包含攻击逻辑。我用以下方式定义了我的类：

class Warrior:
    def __init__(self, energy):
        self.energy = energy


class TemplarKnight(Warrior, HandToHandCombatMixin):
    pass


class CombatMixin:
    def __init__(self):
        self.attacks_cost = {}

    def attack(self, attacker, attack_cost):
        if attacker.energy < attack_cost:
            print('Not enough energy to attack')
        else:
            attacker.energy -= attack_cost
            print('Attack!')


class HandToHandCombatMixin(CombatMixin):
    def __init__(self):
        super().__init__()
        self.attacks_cost['sword_spin'] = 10

    def sword_spin(self, attacker):
        return self.attack(attacker, self.attacks_cost['sword_spin'])

但是当我尝试测试这个设置时，问题就出现了。当我这样做的时候

class TestTemplarKnight(unittest.TestCase):
    def setUp(self):
        self.templar = TemplarKnight(energy=100)

    def test_templar_knight_can_sword_spin(self):
        self.templar.sword_spin(self.warrior)
        self.assertEquals(self.templar.energy, 90)

我明白了

    def sword_spin(self, attacker):
        return self.attack(
>           attacker, self.attacks_cost['sword_spin'])
E       AttributeError: 'TemplarKnight' object has no attribute 'attacks_cost'

Python似乎认为参数self.attacks_cost（在HandToHandCombatMixin类的sword_spin()方法内调用self.attack()）属于TemplarKnight类，而不是HandToHandCombatMixin

我应该如何编写这段代码使Python在HandToHandCombatMixin中查找self.attacks_cost

Answer 1

要正确使用super，所有涉及的类都需要使用它。现在，首先调用Warrior.__init__，但它不使用super，因此HandToHandCombatMixin.__init__永远不会被调用

添加以下内容：

class Warrior:
    def __init__(self, energy, **kwargs):
        super().__init__(**kwargs)
        self.energy = energy


class TemplarKnight(Warrior, HandToHandCombatMixin):
    pass


class CombatMixin:
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.attacks_cost = {}

    def attack(self, attacker, attack_cost):
        if attacker.energy < attack_cost:
            print('Not enough energy to attack')
        else:
            attacker.energy -= attack_cost
            print('Attack!')


class HandToHandCombatMixin(CombatMixin):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.attacks_cost['sword_spin'] = 10

    def sword_spin(self, attacker):
        return self.attack(attacker, self.attacks_cost['sword_spin'])

现在，当您实例化TemplarKnight时，您将保证以正确的顺序调用所有__init__方法。最终，对super()的一次调用将导致object.__init__被调用，在这一点上链最终结束。如果正确处理关键字参数，**kwargs在发生时将为空