【设计模式】2.策略模式

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https://blog.csdn.net/weixin_39190382?type=blog

0. 前言

商场收银软件为例

1. 基础版

total = 0def click_ok(price,num):tot = price * numtotal += totprint('合计：', total)

增加打折

total = 0def click_ok(price,num,dis_num):tot = price * numtotal += totif dis_num == '0': # 正常收费passelif dis_num == '8':total *= 0.8elif dis_num == '7':total *= 0.7elif dis_num == '5':total *= 0.5print('合计：', total)

2. 简单工厂

20250511215044

class cashSuper(ABC):"""收取现金超类"""@abstractmodedef acceptcash(money):"""接收现金抽象类"""passclass cashNormal(cashSuper):"""正常收费子类"""def acceptcash(money):return moneyclass cashRebate(cashSuper):"""打折收费子类"""def cash_rebate(rebate):"""打折"""self.rebate = rebatedef acceptcash(money):return money * self.rebateclass cashReturn(cashSuper):"""返利收费条件"""def cash_return(condition, moneyreturn):self.condition = condition # 返利条件self.moneyreturn = moneyreturndef accpetcash(money):if money >= self.condition:return money - (money-self.condition)*self.moneyreturnreturn money

class CashFactory:@staticmethoddef create_cash_accept(type_str) -> CashSuper:cs = Noneif type_str == "正常收费":cs = CashNormal()elif type_str == "满 300 返 100":cr1 = CashReturn("300", "100")cs = cr1elif type_str == "打 8 折":cr2 = CashRebate("0.8")cs = cr2return cs

3. 策略模式

20250511221305

class cashSuper(ABC):"""收取现金超类"""@abstractmodedef acceptcash(money):"""接收现金抽象类"""passclass cashNormal(cashSuper):"""正常收费子类"""def acceptcash(money):return moneyclass cashRebate(cashSuper):"""打折收费子类"""def cash_rebate(rebate):"""打折"""self.rebate = rebatedef acceptcash(money):return money * self.rebateclass cashReturn(cashSuper):"""返利收费条件"""def cash_return(condition, moneyreturn):self.condition = condition # 返利条件self.moneyreturn = moneyreturndef accpetcash(money):if money >= self.condition:return money - (money-self.condition)*self.moneyreturnreturn money

class CashContext:def __init__(self, cash_super:cashSuper):self.cs = cash_super  # 通过构造方法传入具体的收费策略def get_result(self, money):return self.cs.accept_cash(money)  # 根据收费策略计算结果

需要再客户端判断哪种收费方式，可进行如下修改

4. 策略和简单工厂结合

这样就不用再客户端里面写分类代码了。

# 上下文类
class CashContext:def __init__(self, type: str):self.cs = Noneif type == "正常收费":self.cs = CashNormal()elif type == "满 300 返 100":self.cs = CashReturn("300", "100")elif type == "打 8 折":self.cs = CashRebate("0.8")else:raise ValueError("无效的收费类型")def get_result(self, money: float) -> float:return self.cs.accept_cash(money)

5. 简单工厂 VS 策略和简单工厂结合

客户端

简单工厂

# 客户端代码
from cash_factory import CashFactory, CashSuper  # 必须导入父类 CashSupertype = "满 300 返 100"
money = 350# 客户端需要显式调用工厂，并知道返回的是 CashSuper 类型
csuper = CashFactory.create_cash_accept(type)  # 客户端知道 CashSuper 存在
result = csuper.accept_cash(money)            # 客户端需了解 accept_cash() 方法

策略和简单工厂结合

# 客户端代码
from cash_context import CashContext  # 仅需导入 CashContexttype = "满 300 返 100"
money = 350# 客户端只需与 CashContext 交互
csuper = CashContext(type)           # 完全隐藏 CashSuper 和 CashFactory
result = csuper.get_result(money)    # 统一方法名，隐藏具体实现