usingdefaults.cpp

《24学时精通c++》的光盘内容

//Listing 13.2 Default values in member functions 
#include <iostream>  

// Rectangle class declaration 
class Rectangle 
{ 
public:
     // constructors     
     Rectangle(int width, int height);     
     ~Rectangle(){}     
     void DrawShape(int aWidth, int aHeight,
      bool UseCurrentVals = false) const; 
private:
     int itsWidth;     
     int itsHeight; 
};  

//Constructor implementation 
Rectangle::Rectangle(int width, int height): 
itsWidth(width),       // initializations 
itsHeight(height) 
{}                     // empty body  

// default values used for third parameter 
void Rectangle::DrawShape(
     int width,
     int height,
     bool UseCurrentValue
     ) const 
{
     int printWidth;
     int printHeight;

     if (UseCurrentValue == true)
     {
         printWidth = itsWidth;       // use current class values
         printHeight = itsHeight;
     }
     else
     {
         printWidth = width;         // use parameter values
         printHeight = height;
     }

     for (int i = 0; i<printHeight; i++)
     {
         for (int j = 0; j< printWidth; j++)
         {
             std::cout << "*";
         }
         std::cout << "\n";
     }
 }

// Driver program to demonstrate overloaded functions 
int main() 
{
     // initialize a rectangle to 30,5
     Rectangle theRect(30,5);
     std::cout << "DrawShape(0,0,true)...\n";
     theRect.DrawShape(0,0,true);
     std::cout <<"DrawShape(40,2)...\n";
     theRect.DrawShape(40,2);
     return 0;
}