The application of singleton mode and factory mode in C++ function overloading and rewriting-C++-php.cn

Singleton mode: Provide singleton instances with different parameters through function overloading. Factory pattern: Create different types of objects through function rewriting to decouple the creation process from specific product classes.

C++ 函数重载和重写中单例模式与工厂模式的运用

The application of singleton mode and factory mode in function overloading and rewriting in C

Singleton mode

Function overloading

The singleton mode can be implemented through function overloading. The overloaded function has a different parameter list and thus returns a different instance.

class Singleton { public: static Singleton* getInstance() { if (instance_ == nullptr) { instance_ = new Singleton(); } return instance_; } static Singleton* getInstance(int arg) { if (instance_ == nullptr) { instance_ = new Singleton(arg); } return instance_; } private: Singleton() = default; Singleton(int arg); static Singleton* instance_; };

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Practical case

Create two singleton objects: one with parameters and one without parameters.

int main() { Singleton* instance1 = Singleton::getInstance(); Singleton* instance2 = Singleton::getInstance(10); // 检查两个实例是否相同 if (instance1 == instance2) { std::cout << "两个实例相同" << std::endl; } else { std::cout << "两个实例不相同" << std::endl; } }

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Factory mode

Function rewriting

Factory mode can be implemented through function rewriting. The rewritten function has Different implementations create different objects.

class Product { public: virtual ~Product() {} }; class ConcreteProductA : public Product { // ... }; class ConcreteProductB : public Product { // ... }; class Factory { public: virtual ~Factory() {} virtual Product* createProduct() = 0; }; class ConcreteFactoryA : public Factory { public: Product* createProduct() override { return new ConcreteProductA(); } }; class ConcreteFactoryB : public Factory { public: Product* createProduct() override { return new ConcreteProductB(); } };

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Practical case

Create two factory objects, each object creates a different product type.

int main() { Factory* factory1 = new ConcreteFactoryA(); Product* product1 = factory1->createProduct(); Factory* factory2 = new ConcreteFactoryB(); Product* product2 = factory2->createProduct(); // 检查两个产品类型是否不同 if (typeid(*product1) != typeid(*product2)) { std::cout << "两个产品类型不同" << std::endl; } else { std::cout << "两个产品类型相同" << std::endl; } }

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