建構函式：

生成物件時呼叫建構函式
生成派生類物件時先呼叫基類建構函式在呼叫派生類建構函式

#include <iostream>
using namespace std;

class base
{
public:
    base(){cout<<"base"<<endl;}
    virtual ~base(){}
};

class derived:public base
{
public:
    derived(){cout<<"derived"<<endl;}
    ~derived(){}
};
int main()
{
    base
 
 *point=new derived();
    return 0;
}

輸出結果為：
base
derived

解構函式：

撤銷物件時呼叫解構函式
撤銷派生類物件時，先呼叫派生類的解構函式再呼叫基類的解構函式。

#include <iostream>
using namespace std;

class base
{
public:
    base(){}
    //virtual ~base(){}
    ~base(){cout<<"base"<<endl;}
};

class derived:public base
{
public
 
:
    derived(){}
    ~derived(){cout<<"derived"<<endl;}
};
int main()
{
    derived *p=new derived;
    delete p;
    return 0;
}

輸出結果為：
derived
base

虛擬的解構函式：

基類指標指向派生類物件時，撤銷指標
當基類解構函式不叫virtual關鍵字，則下列程式碼輸出結果為base（只調用基類解構函式）

#include <iostream>
using namespace std;

class base
 

{
public:
    base(){}
    ~base(){cout<<"base"<<endl;}//正常的解構函式
};

class derived:public base
{
public:
    derived(){}
    ~derived(){cout<<"derived"<<endl;}
};
int main()
{
    base *point=new derived();
    delete point;
    return 0;
}

基類指標指向派生類物件時，
當基類解構函式加virtual關鍵字時，撤銷指標先呼叫派生類解構函式再呼叫基類解構函式
輸出結果：
derived
base

#include <iostream>
using namespace std;

class base
{
public:
    base(){}
    virtual ~base(){cout<<"base"<<endl;}//虛擬的解構函式
};

class derived:public base
{
public:
    derived(){}
    ~derived(){cout<<"derived"<<endl;}
};
int main()
{
    base *point=new derived();
    delete point;
    return 0;
}