学步园

class Base<br /> {<br /> public:<br /> virtual void display(std::string strShow = "I am Base class !")<br /> { std::cout << strShow << std::endl; }<br /> virtual ~Base(){}<br /> };<br /> class Derive: public Base<br /> {<br /> public:<br /> virtual void display(std::string strShow = "I am Derive class !")<br /> { std::cout << strShow << std::endl; }<br /> virtual ~Derive(){}<br /> };<br /> int main()<br /> {<br /> Base* pBase = new Derive();<br /> Derive* pDerive = new Derive();<br /> pBase->display();<br /> pDerive->display();<br /> delete pBase;<br /> delete pDerive;<br /> return 0;<br /> }

表面上看是多态，但是我们应该注意到函数的参数，当我们不带参数时，他使用默认的参数。

默认的参数会以静态类型为准，而实际运行时会以真实的类型为准。