Стратегія на C++

/** * The Strategy interface declares operations common to all supported versions * of some algorithm. * * The Context uses this interface to call the algorithm defined by Concrete * Strategies. */ class Strategy { public: virtual ~Strategy() = default; virtual std::string doAlgorithm(std::string_view data) const = 0; }; /** * The Context defines the interface of interest to clients. */ class Context { /** * @var Strategy The Context maintains a reference to one of the Strategy * objects. The Context does not know the concrete class of a strategy. It * should work with all strategies via the Strategy interface. */ private: std::unique_ptr<Strategy> strategy_; /** * Usually, the Context accepts a strategy through the constructor, but also * provides a setter to change it at runtime. */ public: explicit Context(std::unique_ptr<Strategy> &&strategy = {}) : strategy_(std::move(strategy)) { } /** * Usually, the Context allows replacing a Strategy object at runtime. */ void set_strategy(std::unique_ptr<Strategy> &&strategy) { strategy_ = std::move(strategy); } /** * The Context delegates some work to the Strategy object instead of * implementing +multiple versions of the algorithm on its own. */ void doSomeBusinessLogic() const { if (strategy_) { std::cout << "Context: Sorting data using the strategy (not sure how it'll do it)\n"; std::string result = strategy_->doAlgorithm("aecbd"); std::cout << result << "\n"; } else { std::cout << "Context: Strategy isn't set\n"; } } }; /** * Concrete Strategies implement the algorithm while following the base Strategy * interface. The interface makes them interchangeable in the Context. */ class ConcreteStrategyA : public Strategy { public: std::string doAlgorithm(std::string_view data) const override { std::string result(data); std::sort(std::begin(result), std::end(result)); return result; } }; class ConcreteStrategyB : public Strategy { std::string doAlgorithm(std::string_view data) const override { std::string result(data); std::sort(std::begin(result), std::end(result), std::greater<>()); return result; } }; /** * The client code picks a concrete strategy and passes it to the context. The * client should be aware of the differences between strategies in order to make * the right choice. */ void clientCode() { Context context(std::make_unique<ConcreteStrategyA>()); std::cout << "Client: Strategy is set to normal sorting.\n"; context.doSomeBusinessLogic(); std::cout << "\n"; std::cout << "Client: Strategy is set to reverse sorting.\n"; context.set_strategy(std::make_unique<ConcreteStrategyB>()); context.doSomeBusinessLogic(); } int main() { clientCode(); return 0; } 

Client: Strategy is set to normal sorting. Context: Sorting data using the strategy (not sure how it'll do it) abcde Client: Strategy is set to reverse sorting. Context: Sorting data using the strategy (not sure how it'll do it) edcba