demo2_polymorphism.py

"""
demo2: 多态 (Polymorphism)
场景：支付系统——不同支付方式，同一个接口
"""
from abc import ABC, abstractmethod


class Payment(ABC):
    @abstractmethod
    def pay(self, amount: float) -> str:
        pass
    
    @abstractmethod
    def get_name(self) -> str:
        pass


class WeChatPay(Payment):
    def pay(self, amount: float) -> str:
        return f"微信支付: {amount:.2f} (从零钱扣款)"
    
    def get_name(self) -> str:
        return "微信支付"


class Alipay(Payment):
    def pay(self, amount: float) -> str:
        return f"支付宝: {amount:.2f} (从余额扣款)"
    
    def get_name(self) -> str:
        return "支付宝"


class CreditCard(Payment):
    def __init__(self, card_number: str):
        self.card_number = card_number[-4:]
    
    def pay(self, amount: float) -> str:
        return f"信用卡(尾号{self.card_number}): {amount:.2f} (已授权)"
    
    def get_name(self) -> str:
        return f"信用卡({self.card_number})"


def process_payment(payment: Payment, amount: float):
    print(f"[{payment.get_name()}] {payment.pay(amount)}")


if __name__ == "__main__":
    print("=== 多态演示: 支付系统 ===\n")
    payments = [WeChatPay(), Alipay(), CreditCard("6222021234567890")]
    for p in payments:
        process_payment(p, 99.50)
    
    print(f"\n--- 多态的好处 ---")
    print("1. 新增支付方式只需继承Payment, 不用改process_payment")
    print("2. 所有支付方式遵循同一个接口")
    print("3. 可以用列表统一管理不同类型的对象")