fig10_07.cpp

来自「《c＋＋大学教程》源码」· C++ 代码 · 共 48 行

// Fig. 10.7: fig10_07.cpp
// Attempting to invoke derived-class-only member functions
// through a base-class pointer.
#include "point.h"   // Point class definition
#include "circle.h"  // Circle class definition

int main()
{
   Point *pointPtr = 0;
   Circle circle( 120, 89, 2.7 );

   // aim base-class pointer at derived-class object
   pointPtr = &circle;

   // invoke base-class member functions on derived-class
   // object through base-class pointer
   int x = pointPtr->getX();
   int y = pointPtr->getY();
   pointPtr->setX( 10 );
   pointPtr->setY( 10 );
   pointPtr->print();

   // attempt to invoke derived-class-only member functions
   // on derived-class object through base-class pointer   
   double radius = pointPtr->getRadius();
   pointPtr->setRadius( 33.33 );
   double diameter = pointPtr->getDiameter();
   double circumference = pointPtr->getCircumference();
   double area = pointPtr->getArea();

   return 0;

} // end main

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