如何在C++中创建一个类？

class MyClass {
public:
    int myVariable;

    void myFunction() {
        // 函数体
    }
};

class Person {
private:
    std::string name;
    int age;

public:
    void setName(const std::string& newName) {
        name = newName;
    }

    void setAge(int newAge) {
        if (newAge >= 0) {
            age = newAge;
        }
    }

    std::string getName() const {
        return name;
    }

    int getAge() const {
        return age;
    }
};

class Car {
private:
    std::string model;
    int year;

public:
    // 构造函数
    Car(const std::string& carModel, int carYear) : model(carModel), year(carYear) {}

    // 析构函数
    ~Car() {
        // 清理操作
    }

    // 其他成员函数...
};

class Rectangle {
private:
    double length;
    double width;

public:
    Rectangle(double l, double w) : length(l), width(w) {}

    double area() const {
        return length * width;
    }
};

// 在类体外定义成员函数
double Rectangle::perimeter() const {
    return 2 * (length + width);
}

class Counter {
private:
    static int count;

public:
    Counter() {
        ++count;
    }

    ~Counter() {
        --count;
    }

    static int getCount() {
        return count;
    }
};

// 静态成员变量需要在类外初始化
int Counter::count = 0;

class Box {
private:
    double width;

public:
    Box(double w) : width(w) {}

    friend void printWidth(const Box& box);
};

void printWidth(const Box& box) {
    std::cout << "Width of box: " << box.width << std::endl;
}

class Animal {
public:
    virtual void makeSound() const {
        std::cout << "The animal makes a sound." << std::endl;
    }
};

class Dog : public Animal {
public:
    void makeSound() const override {
        std::cout << "The dog barks." << std::endl;
    }
};

class Cat : public Animal {
public:
    void makeSound() const override {
        std::cout << "The cat meows." << std::endl;
    }
};

int main() {
    Animal* animal1 = new Dog();
    Animal* animal2 = new Cat();

    animal1->makeSound(); // 输出: The dog barks.
    animal2->makeSound(); // 输出: The cat meows.

    delete animal1;
    delete animal2;

    return 0;
}