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#include<iostream> using namespace std; class A { public: A(){cout << "Hello world\n";} }; class B:public A { }; int main() { A *c = new B;//这里不能写成B *c = new A; return 0; } 运行结果： [root@bogon c++]# ./a.out Hello world 运行结果表明执行了A的构造函数 new B的执行过程：首先调用operator new 分配足够的空间，然后执行A的构造函数，B的构造函数。 #include using namespace std; class A { public: A(){cout << "Hello world\n";} ~A() {cout << "fare\n"; } }; class B:public A { public: B() {cout << "hi\n";} ~B() {cout << "Bye\n";} }; int main() { A *c = new B; delete c; return 0; } 运行结果; [root@bogon c++]# ./a.out Hello world hi fare #include using namespace std; class A { public: A(){cout << "Hello world\n";} virtual ~A() {cout << "fare\n"; } }; class B:public A { public: B() {cout << "hi\n";} ~B() {cout << "Bye\n";} }; int main() { A *c = new B; delete c; return 0; } 运行结果： [root@bogon c++]# ./a.out Hello world hi Bye fare 由此可见析构函数应尽量声明为虚函数！构造函数不能为虚函数。无论构造函数还是析构函数尽量不要调用虚函数！ 2016.9.11点击(此处)折叠或打开
#include<iostream> using namespace std; class S { public: S(){cout << "Hello world";fun();} virtual void fun(){cout << "funS";} ~S(){cout << "Bye";} }; class Derived :public S { public: Derived(){cout << "hi";} virtual void fun(){cout << "funDe";} virtual ~Derived(){cout << "farewell";} }; int main() { Derived *de = new Derived(); delete de; return 0; } 运行结果： [root@bogon ~]# ./a.out Hello worldfunShifarewellBye[root@bogon ~]# <script>window._bd_share_config={"common":{"bdSnsKey":{},"bdText":"","bdMini":"2","bdMiniList":false,"bdPic":"","bdStyle":"0","bdSize":"16"},"share":{}};with(document)0[(getElementsByTagName('head')[0]||body).appendChild(createElement('script')).src='http://bdimg.share.baidu.com/static/api/js/share.js?v=89860593.js?cdnversion='+~(-new Date()/36e5)];</script> 阅读(96) | 评论(0) | 转发(0) | 1上一篇： 排序算法稳定性
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