Question

MFC上Rectangle类的诡异问题，无法初始化对象，而换一个类，比如Rect，代码相同却可以初始化！

Shape类 同时还有一个Circle类，Circle没问题
#ifndef Shape_h
#define Shape_h
class Shape
{
public:
virtual double ZhouChang()=0;
virtual double Area()=0;
};
#endif
Rectangle.h
#include "Shape.h"

class Rectangle:public Shape
{
private:
int x,y;
public:
Rectangle(int,int);
double ZhouChang();
double Area();
};

Rectangle.cpp
#include "StdAfx.h"
#include "Rectangle.h"

Rectangle::Rectangle(int x,int y)
{
this->x=x;
this->y=y;
}
double Rectangle::ZhouChang()
{
return (x+y)*2;
}
double Rectangle::Area()
{
return x*y;
}

OnDraw 函数 已添加头文件 Rectangle.h
void CEx3_ClassShapeView::OnDraw(CDC* pDC)
{
CEx3_ClassShapeDoc* pDoc = GetDocument();
ASSERT_VALID(pDoc);
// TODO: add draw code for native data here

double TotalArea=0;
Circle c1(10.0);
Circle c2(20.0);
Rectangle r1(3,3);
Shape *pS[]={&c1,&c2,&r1};
for (int i=0;i<3;i++)
{
TotalArea+=pS[i]->Area();
}
CString str;
str.Format("总面积为：%.2f",TotalArea);
pDC->TextOut(100,100,str);
}

Answer 1

加一个命名空间或者换个名字吧，命名冲突了！

Answer 2

这个是Win32API

The Rectangle function draws a rectangle. The rectangle is outlined by using the current pen and filled by using the current brush.

BOOL Rectangle(
HDC hdc, // handle to DC
int nLeftRect, // x-coord of upper-left corner of rectangle
int nTopRect, // y-coord of upper-left corner of rectangle
int nRightRect, // x-coord of lower-right corner of rectangle
int nBottomRect // y-coord of lower-right corner of rectangle
);

Requirements
Windows NT/2000/XP/Vista: Included in Windows NT 3.1 and later.
Windows 95/98/Me: Included in Windows 95 and later.
Header: Declared in Wingdi.h; include Windows.h.
Library: Use Gdi32.lib.

Answer 3

Rectangle 是WIN32 API中的一个 结构体。你最好改一下名字。