C++中vitual的用法总结

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一、修饰成员函数

#include <iostream>using namespace std;class A{public:A(){}public:    virtual void func1(){ cout << "A vitual"; }    virtual void func2()    {        func1();    }};class B :public A{public:B(){}public:     void func1(){ cout << "B vitual"; }     void func2(){        func1();    }};int main(){    A *a = new B();    a->func2();    while (1);    return 0;}

输出结果：
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二、修饰类

#include <iostream>using namespace std;class A{public:       A()    {         cout << "A构造" << endl;    }    ~A()    {         cout << "A析构" << endl;     }};class B : virtual public A{public:        B()    {         cout << "B构造" << endl;     }    ~B()    {         cout << "B析构" << endl;    }};class C : virtual public A{public:         C()    {         cout << "C构造" << endl;    }    ~C()    {         cout << "C析构" << endl;    }};class D : public B, public C{public:                D()    {         cout << "D构造" << endl;     }    ~D()    {         cout << "D析构" << endl;     }};int main(){    D *d = new D();    delete d;    while (1);    return 0;}

执行结果:
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类没有被vitual修饰时：

#include <iostream>using namespace std;class A{public:       A()    {         cout << "A构造" << endl;    }    ~A()    {         cout << "A析构" << endl;     }};class B : public A{public:        B()    {         cout << "B构造" << endl;     }    ~B()    {         cout << "B析构" << endl;    }};class C :  public A{public:         C()    {         cout << "C构造" << endl;    }    ~C()    {         cout << "C析构" << endl;    }};class D : public B, public C{public:                D()    {         cout << "D构造" << endl;     }    ~D()    {         cout << "D析构" << endl;     }};int main(){    D *d = new D();    delete d;    while (1);    return 0;}

执行结果：
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三、vitual修饰析构函数

#include <iostream>using namespace std;class A{public:    A()    {        cout << "construct A" << endl;    }    virtual ~A()    {        cout << "destory A" << endl;    }   }; class B : public A{public:    B()    {                  cout << "construct B" << endl;    }    virtual ~B()    {                      cout << "destory B" << endl;    }   };int main(){       A *a = new B();    delete a;    while (10);    return 0;}

执行结果：

这里写图片描述

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