point.h:
enum Boolean {false, true};
class Location {
protected: // allows derived class to access private data
int X;
int Y;
public: // these functions can be accessed from outside
Location(int InitX, int InitY);
int GetX();
int GetY();
};
class Point : public Location {
protected:
Boolean Visible; // classes derived from Point will need access
public:
Point(int InitX, int InitY); // constructor
void Show();
void Hide();
Boolean IsVisible();
void MoveTo(int NewX, int NewY);
};
////////////////////////////////////////////////////////////////////////////////
circle.cpp:
#include <graphics.h> // graphics library declarations
#include "point.h" // Location and Point class declarations
#include <conio.h> // for getch() function
class Circle : Point { // derived privately from class Point
// and ultimately from class Location
int Radius; // private by default
public:
Circle(int InitX, int InitY, int InitRadius);
void Show(void);
void Hide(void);
void Expand(int ExpandBy);
void MoveTo(int NewX, int NewY);
void Contract(int ContractBy);
};
Circle::Circle(int InitX, int InitY, int InitRadius) : Point(InitX,InitY)
{
Radius = InitRadius;
};
void Circle::Show(void)
{
Visible = true;
circle(X, Y, Radius); // draw the circle
}
void Circle::Hide(void)
{
unsigned int TempColor; // to save current color
TempColor = getcolor(); // set to current color
setcolor(getbkcolor()); // set drawing color to background
Visible = false;
circle(X, Y, Radius); // draw in background color to erase
setcolor(TempColor); // set color back to current color
};
void Circle::Expand(int ExpandBy)
{
Hide(); // erase old circle
Radius += ExpandBy; // expand radius
if (Radius < 0) // avoid negative radius
Radius = 0;
Show(); // draw new circle
};
void Circle::Contract(int ContractBy)
{
Expand(-ContractBy); // redraws with (Radius - ContractBy)
};
void Circle::MoveTo(int NewX, int NewY)
{
Hide(); // erase old circle
X = NewX; // set new location
Y = NewY;
Show(); // draw in new location
};
main() // test the functions
{
// initialize the graphics system
int graphdriver = DETECT, graphmode;
initgraph(&graphdriver, &graphmode, "..\\bgi");
Circle MyCircle(100, 200, 50); // declare a circle object
MyCircle.Show(); // show it
getch(); // wait for keypress
MyCircle.MoveTo(200, 250); // move the circle (tests hide
// and show also)
getch();
MyCircle.Expand(50); // make it bigger
getch();
MyCircle.Contract(75); // make it smaller
getch();
closegraph();
return 0;
}
错误提示:
Linking CIRCLE.EXE:
Linker Error: Undefined symbol _closegraph in module CIRCLE.CPP
Linker Error: Undefined symbol _initgraph in module CIRCLE.CPP
Linker Error: Undefined symbol _setcolor in module CIRCLE.CPP
Linker Error: Undefined symbol _circle in module CIRCLE.CPP
Linker Error: Undefined symbol _getbkcolor in module CIRCLE.CPP
Linker Error: Undefined symbol _getcolor in module CIRCLE.CPP
Linker Error: Undefined symbol Point::Point(int,int) in module CIRCLE.CPP
谢谢
