一次策略模式的代码实践

需求清单

1.单个商品购买数量大于20个，订单折扣10%

2.商品种类超过或等于5个，订单折扣20%

3.订单总价超过10000元，订单折扣15%

4.客户积分达到2000，折扣7%

目前折扣计算方式有4种，为了提高代码的扩展性，灵活性，使用策略模式进行编码

from typing import List

from collections import namedtuple

# 客户类，类属性，姓名 积分

Customer = namedtuple('Customer', 'name score')

class LineItem:

"""款项类"""

def __init__(self, product: str, count: int, price: float) -> None:

self.product = product

self.count = count

self.price = price

self.total = round(self.price * self.count, 2)

def __repr__(self):

return f'商品名称：{self.product}，单价：{self.price}元，数量：{self.count}，总价：{self.total}元'

# Order类，上下文

class Order:

"""订单类"""

def __init__(self, customer: Customer, cart: List[LineItem], promotion: callable = None) -> None:

self.customer = customer

self.cart = cart

self._promotion = promotion

self.total = sum(c.total for c in self.cart)

self._v = 0

@property

def promotion(self) -> None:

pass

@promotion.setter

def promotion(self, p: callable) -> None:

if not callable(p):

raise ValueError('p不是一个可调用对象')

self._promotion = p

def due(self) -> float:

if not self._promotion:

discount = 0

else:

discount = self._promotion(self)

return self.total - discount

def info(self) -> None:

for line in self.cart:

print(line)

print(f'总价：{self.total}，折扣价：{self.due()}')

print('*' * 20)

print()

# 具体折扣计算函数

def discount_single_product_num_gte_20(order: Order) -> float:

"""单个商品购买数量大于20个，订单折扣10%"""

if any(c.count >= 20 for c in order.cart):

return order.total * 0.10

return 0

def discount_product_kind_gte_5(order: Order) -> float:

"""商品种类超过5个，订单折扣20%"""

if len(order.cart) >= 5:

return order.total * 0.20

return 0

def discount_total_gte_10000(order: Order) -> float:

"""订单总价超过10000元，订单折扣15%"""

if order.total >= 10000:

return order.total * 0.15

return 0

def discount_score_gte_2000(order: Order) -> float:

"""客户积分达到2000，折扣7%"""

if order.customer.score >= 2000:

return order.total * 0.07

return 0

if __name__ == '__main__':

c1 = Customer('客户1', 1000)

c2 = Customer('客户1', 2000)

# 测试用例

# 单个商品购买数量大于20个，订单折扣10%

i1 = LineItem('MacBook', 1, 7000)

i2 = LineItem('扩展坞', 20, 50)

i3 = LineItem('Usb type C', 30, 40.0)

cart1 = [i2]

cart2 = [i1, i3]

order1 = Order(c1, cart1, discount_single_product_num_gte_20)

order1.info()

order2 = Order(c1, cart2, discount_single_product_num_gte_20)

order2.info()

# 商品种类超过5个，订单折扣20%

i1 = LineItem('MacBook', 1, 7000)

i2 = LineItem('扩展坞', 20, 50)

i3 = LineItem('Usb type C1', 30, 40.0)

i4 = LineItem('Usb type C2', 20, 40.0)

i5 = LineItem('Usb type C3', 10, 40.0)

cart3 = [i1, i2, i3, i4, i5]

order3 = Order(c1, cart1, discount_product_kind_gte_5)

order3.info()

# 订单总价超过10000元，订单折扣15%

order4 = Order(c1, cart3, discount_total_gte_10000)

order4.info()

# 客户积分达到2000，折扣7%

order5 = Order(c2, cart1, discount_score_gte_2000)

order5.info()

# 客人希望使用另一个种折扣方式，因为更划算

order5.promotion = discount_single_product_num_gte_20

order5.info()