虚函数缺省实参

Class Base
{
public:
    virtual void foo( int ival = 1024 )
    {
        cout << "Base::foo() -- ival: " << ival << endl;
    }
};

class Derived : public Base
{
public:
    virtual void foo( int ival = 2048 )
    {
        cout << "Derived::foo() -- ival: " << ival << endl;
    }
};

int main()
{
    Derived *pd = new Derived;
    Base *pb = pd;
    
    pb->foo();
    pd->foo();
    
    delete pd;
    pb = NULL;

    return 0;
}

虚函数的缺省实参不是在运行时刻决定的,而是在编译时刻根据被调用函数的对象的类型决定的!

上述输出为:

   Derived::foo() -- ival: 1024
   Derived::foo() -- ival: 2048

posted @ 2016-10-12 09:12  bonelee  阅读(305)  评论(0编辑  收藏  举报