overring virtual functions

原创于 2011-12-12 13:39:58 发布 · 422 阅读

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#include #delete #class

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本文探讨了C++中类继承的使用，特别关注于如何通过模板和多态性来实现更灵活和强大的面向对象编程。通过实例展示了如何定义基类和派生类，以及如何利用虚函数实现多态。同时，介绍了模板的运用，展示其在泛型编程中的优势。

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#include <iostream>
#include <complex>

using namespace std;

class Base
{
public:

  virtual void f( int );
  virtual void f(double);
  virtual void g(int i = 10);
};


void Base::f( int )
{
  cout << "Base::f(int)" << endl;
}

void Base::f( double )
{
  cout << "Base::f(double)" << endl;
}

void Base::g( int i )
{
  cout << i << endl;
}

class Derived: public Base
{
public:
// using Base::f
  void f(complex<double>); // hide the Base f.
  // overrides Base::g but changes the default parameter.
  void g( int i = 20 );
};

void Derived::f(complex<double>)
{
  cout << "Derived::f(complex)" << endl;
}

void Derived::g(int i)
{
 cout << "Derived::g() " << i << endl;
}

void main() // int
{

  Base    b;
  Derived d;
  Base*   pb = new Derived;

  b.f(1.0); // Base::f(double)

  d.f(1.0); // Derived::f(complex)

  pb->f(1.0); // Base::f( double ) notice? *****

  b.g(); // 10

  d.g(); //Derived::g() 20

  pb->g(); //Derived::g() 10 notice?  *****
  delete pb; // unsafe ?


}