实践如下：

#include 
     
      using namespace std;class Service {public:    // 有一个虚函数即为抽象类    int id;    // 不定义虚析构函数 会报右侧异常：@suppress("Class has a virtual method and non-virtual destructor")    virtual ~Service(){}    virtual double calc()=0;    int aa(){        return 11;    }};class AService: public Service {public:    //virtual ~AService(){}    double calc() {        // 操作抽象类中定义的字段        id = 100;        cout << "id：" << id << endl;        cout << "AService 100~~~" << endl;        return 100;    }};class BService: public Service {public:    //virtual ~BService(){}    double calc() {        cout << "BService 200~~~" << endl;        return 200;    }};int main() {    cout << "抽象类 实践：" << endl;    Service *s = new AService();    s->calc();    cout << "\n抽象类 end." << endl;    return 0;}
     

结果：