Application and precautions of object-oriented design pattern in C++

Applying object-oriented design patterns in C++ can improve the maintainability and reusability of code. The singleton pattern ensures that there is only one class instance, and the factory pattern is responsible for creating object instances without specifying a specific class. When applying design patterns, be careful not to overuse them, understand their intent, pay attention to efficiency, choose lightweight patterns, and combine patterns to create flexible solutions.

Application and precautions of object-oriented design pattern in C++

Object-oriented design pattern is a set of proven solutions for solving software problems Common challenges in design. Applying these patterns in C++ can significantly improve the maintainability, scalability, and reusability of your code.

Singleton mode

The singleton mode ensures that only one instance of the class exists. This is useful in situations where global access to a single object is required.

class Singleton {
private:
    Singleton() {}  // 私有构造函数

    static Singleton* instance;  // 指向单例实例的静态指针

public:
    static Singleton* getInstance() {
        if (!instance) {
            instance = new Singleton();  // 如果没有实例，则创建实例
        }
        return instance;
    }
};

// 实战案例
int main() {
    Singleton* singleton1 = Singleton::getInstance();
    Singleton* singleton2 = Singleton::getInstance();

    if (singleton1 == singleton2) {
        // singleton1 和 singleton2 指向同一个对象
    }
}

Factory Pattern

The factory pattern is responsible for creating instances of objects without specifying their exact class. This allows dynamic selection of classes to be instantiated at runtime.

class Shape {
public:
    virtual void draw() = 0;  // 绘制形状的抽象方法
};

class Square : public Shape {
public:
    void draw() override {
        // 绘制正方形
    }
};

class Circle : public Shape {
public:
    void draw() override {
        // 绘制圆形
    }
};

class ShapeFactory {
public:
    static Shape* createShape(int shapeType) {
        switch (shapeType) {
            case 0: return new Square();
            case 1: return new Circle();
            default: return nullptr;
        }
    }
};

// 实战案例
int main() {
    Shape* shape = ShapeFactory::createShape(0);  // 创建正方形
    shape->draw();  // 绘制正方形
}

NOTES AND NOTES

When applying design patterns in C++, please note the following considerations:

• Don’t overuse: Design Patterns are tools, not universal solutions. Use them only when necessary.
• Understand its intent: Before applying a pattern, make sure you understand its purpose and limitations.
• Note on efficiency: Design patterns may require additional overhead. Carefully consider their performance impact when needed.
• Lightweight design: Lightweight patterns, such as factory patterns, are preferred as they have minimal impact on the code.
• Combined Patterns: By combining different patterns, you can create flexible and scalable solutions.

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