保證基類的也被調(diào)用。什么情況下使用比較好呢。

#include <iostream>
using namespace std;
class Base{
    private:
        int num1;
    public:
        Base():num1(10)
        {
        }
        virtual ~Base()
        {
            cout<<"base"<<endl;
        }
};
class Dervied:public Base{
    private:
        int num2;
    public:
        Dervied():num2(1)
        {
        }
        ~Dervied()
        {
            cout<<"Dervied"<<endl;
        }
};
int main()
{
    Base *pBase = new Dervied();
    delete pBase;
}

結(jié)果會(huì)
Dervied
Base
#include<iostream>
using namespace std;

class ClxBase
{
    public:
       ClxBase() {};
       ~ClxBase() {cout<<"Do base class destruct"<<endl;};

};

class ClxDerived : public ClxBase
{
    public:
       ClxDerived() {};
       ~ClxDerived() { cout << "Do derived class destruct!" << endl; };

};


int main()
{

    ClxBase *pTest = new ClxDerived;
    ClxDerived derived;

    delete pTest;

}
另一個(gè)例子輸出的卻是 :
Do base class destruct
Do derived class destruct!
Do base class destruct

說明了兩個(gè)問題，只想派生類對(duì)象的基類指針需要基類聲明虛系構(gòu)函數(shù)才能調(diào)用派生類指針，而派生類對(duì)象卻不用基類聲明虛系構(gòu)函數(shù)就能調(diào)用派生類指針