C++设计模式-策略模式

支付策略 #include <iostream> #include <memory> #include <unordered_map> #include <vector> #include <ctime> // 基础策略接口 class PaymentStrategy { public: virtual ~PaymentStrategy() = default; virtual std::string name() const = 0; virtual bool validate(double amount, const std::string& currency) const = 0; virtual void pay(double amount, const std::string& currency) const = 0; virtual double calculate_fee(double amount) const = 0; }; // 策略工厂系统 class StrategyFactory { public: using StrategyCreator = std::function<std::unique_ptr<PaymentStrategy>()>; static StrategyFactory& instance() { static StrategyFactory instance; return instance; } void register_strategy(const std::string& id, StrategyCreator creator) { creators_[id] = creator; } std::unique_ptr<PaymentStrategy> create(const std::string& id) const { if (auto it = creators_.find(id); it != creators_.end()) { return it->second(); } return nullptr; } std::vector<std::string> available_strategies() const { std::vector<std::string> names; for (const auto& [id, _] : creators_) { names.push_back(id); } return names; } private: std::unordered_map<std::string, StrategyCreator> creators_; }; // 自动注册宏 #define REGISTER_PAYMENT_STRATEGY(StrategyClass, strategy_id) \ namespace { \ struct AutoRegister_##StrategyClass { \ AutoRegister_##StrategyClass() { \ StrategyFactory::instance().register_strategy( \ strategy_id, \ []{ return std::make_unique<StrategyClass>(); } \ ); \ } \ }; \ AutoRegister_##StrategyClass auto_reg_##StrategyClass; \ } // 微信支付策略 class WechatPayStrategy : public PaymentStrategy { const double max_amount_ = 50000.0; // 单笔最大金额 public: std::string name() const override { return "WeChat Pay"; } bool validate(double amount, const std::string& currency) const override { return currency == "CNY" && amount <= max_amount_; } void pay(double amount, const std::string& currency) const override { std::cout << "微信支付成功\n" << "金额: ¥" << amount << "\n" << "请在小程序确认支付" << std::endl; } double calculate_fee(double amount) const override { return amount * 0.001; // 0.1%手续费 } }; REGISTER_PAYMENT_STRATEGY(WechatPayStrategy, "wechat_pay"); // PayPal策略 class PayPalStrategy : public PaymentStrategy { const std::vector<std::string> supported_currencies_{"USD", "EUR", "GBP"}; public: std::string name() const override { return "PayPal"; } bool validate(double amount, const std::string& currency) const override { return std::find(supported_currencies_.begin(), supported_currencies_.end(), currency) != supported_currencies_.end(); } void pay(double amount, const std::string& currency) const override { std::cout << "Processing PayPal payment\n" << "Amount: " << currency << " " << amount << "\n" << "Redirecting to PayPal login..." << std::endl; } double calculate_fee(double amount) const override { return std::max(0.3, amount * 0.05); // 5% + $0.3 } }; REGISTER_PAYMENT_STRATEGY(PayPalStrategy, "paypal"); // 比特币策略（带实时汇率） class BitcoinStrategy : public PaymentStrategy { // 模拟实时汇率获取 double get_bitcoin_price() const { static const double BASE_PRICE = 45000.0; // 基础价格 // 模拟价格波动 return BASE_PRICE * (1.0 + 0.1 * sin(time(nullptr) % 3600)); } public: std::string name() const override { return "Bitcoin"; } bool validate(double amount, const std::string& currency) const override { return currency == "BTC" || currency == "USD"; } void pay(double amount, const std::string& currency) const override { if (currency == "USD") { double btc_amount = amount / get_bitcoin_price(); std::cout << "Converting USD to BTC: " << "₿" << btc_amount << std::endl; amount = btc_amount; } std::cout << "区块链交易确认中...\n" << "转账金额: ₿" << amount << "\n" << "预计确认时间: 10分钟" << std::endl; } double calculate_fee(double amount) const override { return 0.0001 * get_bitcoin_price(); // 固定矿工费 } }; REGISTER_PAYMENT_STRATEGY(BitcoinStrategy, "bitcoin"); // 支付处理器 class PaymentProcessor { std::unordered_map<std::string, std::unique_ptr<PaymentStrategy>> strategies_; public: void load_strategy(const std::string& id) { if (auto strategy = StrategyFactory::instance().create(id)) { strategies_[id] = std::move(strategy); } } void process_payment(const std::string& currency, double amount) { auto strategy = select_strategy(currency, amount); if (!strategy) { throw std::runtime_error("No available payment method"); } std::cout << "\n=== 支付方式: " << strategy->name() << " ===" << "\n金额: " << currency << " " << amount << "\n手续费: " << strategy->calculate_fee(amount) << "\n-------------------------" << std::endl; strategy->pay(amount, currency); } private: PaymentStrategy* select_strategy(const std::string& currency, double amount) { // 选择优先级：本地支付 > 国际支付 > 加密货币 for (auto& [id, strategy] : strategies_) { if (id == "wechat_pay" && strategy->validate(amount, currency)) { return strategy.get(); } } for (auto& [id, strategy] : strategies_) { if (id == "alipay" && strategy->validate(amount, currency)) { return strategy.get(); } } for (auto& [id, strategy] : strategies_) { if (strategy->validate(amount, currency)) { return strategy.get(); } } return nullptr; } }; // 使用示例 int main() { PaymentProcessor processor; // 加载所有注册的支付方式 for (const auto& id : StrategyFactory::instance().available_strategies()) { processor.load_strategy(id); } // 人民币支付 try { processor.process_payment("CNY", 200.0); processor.process_payment("CNY", 60000.0); // 应触发异常 } catch (const std::exception& e) { std::cerr << "支付失败: " << e.what() << std::endl; } // 美元支付 processor.process_payment("USD", 500.0); // 比特币支付 processor.process_payment("BTC", 0.1); processor.process_payment("USD", 1000.0); // 自动转换为BTC return 0; } 代码解析 策略扩展机制 REGISTER_PAYMENT_STRATEGY(WechatPayStrategy, "wechat_pay"); 自动注册：通过宏实现新策略的零配置接入唯一标识：每个策略有唯一的注册ID（如wechat_pay） 微信支付实现 class WechatPayStrategy : public PaymentStrategy { bool validate(...) { /* 校验人民币 */ } void pay(...) { /* 微信特有流程 */ } }; 本地化支持：仅接受人民币移动支付流程：模拟小程序支付场景 PayPal国际支付 class PayPalStrategy : public PaymentStrategy { bool validate(...) { /* 支持多币种 */ } void pay(...) { /* 跳转PayPal */ } }; 多币种支持：USD/EUR/GBP典型手续费模型：固定费用+百分比 比特币支付 class BitcoinStrategy : public PaymentStrategy { double get_bitcoin_price() { /* 模拟实时价格 */ } void pay(...) { /* 自动转换法币 */ } }; 加密货币支持：直接接受BTC或自动转换USD动态手续费：基于当前币价计算矿工费 智能策略选择 PaymentStrategy* select_strategy(...) { // 优先选择本地支付方式 // 次选国际支付 // 最后考虑加密货币 } 业务优先级：体现支付方式选择策略动态路由：根据金额和币种自动路由 执行结果示例 === 支付方式: WeChat Pay === 金额: CNY 200 手续费: 0.2 ------------------------- 微信支付成功 金额: ¥200 请在小程序确认支付 支付失败: No available payment method === 支付方式: PayPal === 金额: USD 500 手续费: 25.3 ------------------------- Processing PayPal payment Amount: USD 500 Redirecting to PayPal login... === 支付方式: Bitcoin === 金额: BTC 0.1 手续费: 4.5 ------------------------- 区块链交易确认中... 转账金额: ₿0.1 预计确认时间: 10分钟 === 支付方式: Bitcoin === 金额: USD 1000 手续费: 4.5 ------------------------- Converting USD to BTC: ₿0.0221132 区块链交易确认中... 转账金额: ₿0.0221132 预计确认时间: 10分钟 待扩展

新增策略步骤：

继承PaymentStrategy实现新类实现所有纯虚函数使用REGISTER_PAYMENT_STRATEGY注册

动态配置：

// 示例：从JSON加载策略配置 void load_config(const json& config) { for (auto& item : config["strategies"]) { auto strategy = factory.create(item["id"]); strategy->configure(item["params"]); add_strategy(std::move(strategy)); } }

混合支付：

class SplitPaymentStrategy : public PaymentStrategy { // 支持多个策略分摊支付 void pay(...) override { credit_card_->pay(part1, currency); crypto_->pay(part2, currency); } };