c++ - 我构造子类对象的方式有什么问题？

Question

这是我的子类:

class BackGround :public Object{
public:
BackGround(int y){
    character.Load(_T("wallpaper.png"));
    x = 0;
    this->y = y;
    direct = 0;
    width = 1200;
    height = 375;
}
};

我的基类:

class Object{
public:
CImage character;     
int x;             
int y;
int direct;       
int speed;
int width;      
int height;
int Xcenter;
int Ycenter;

Object(){}

void draw(HDC hDC){
    character.Draw(hDC, x, y, width, height, 0, direct*height,width, height);
}
};

当我创建 BackGround 类的对象时， 背景 Bg1(0); 背景 Bg2(-WINDOW_HEIGHT);

出现错误:

1>  MainFrm.cpp
1>c:\users\desktop\mfcgame\mfcgame\childview.h(46): error C2059: syntax error: 'const'
1>c:\users\desktop\mfcgame\mfcgame\childview.h(47): error C2059: syntax error:“-”
1>  MFCGame.cpp
1>c:\users\desktop\mfcgame\mfcgame\childview.h(46): error C2059: syntax error: 'const'
1>c:\users\desktop\mfcgame\mfcgame\childview.h(47): error C2059: syntax error:“-”
1>  ChildView.cpp
1>c:\users\desktop\mfcgame\mfcgame\childview.h(46): error C2059: syntax error: 'const'
1>c:\users\desktop\mfcgame\mfcgame\childview.h(47): error C2059: syntax error:“-”
1>c:\users\desktop\mfcgame\mfcgame\childview.cpp(67): error C2228: left of '.draw' must have class/struct/union type
1>c:\users\desktop\mfcgame\mfcgame\childview.cpp(68): error C2228: left of '.draw' must have class/struct/union type
1>c:\users\desktop\mfcgame\mfcgame\childview.cpp(116): error C2228: left of '.y' must have class/struct/union type
1>c:\users\desktop\mfcgame\mfcgame\childview.cpp(118): error C2228: left of '.y' must have class/struct/union type
1>c:\users\desktop\mfcgame\mfcgame\childview.cpp(120): error C2228: left of '.y' must have class/struct/union type
1>c:\users\desktop\mfcgame\mfcgame\childview.cpp(122): error C2228: left of '.y' must have class/struct/union type

Answer 1

我觉得你有

class CChildView : public CWnd
{
    // ...
    BackGround Bg1(0);                // Line 46
    BackGround Bg2(-WINDOW_HEIGHT);   // Line 47
};

这是声明成员变量的错误语法。
(编译器认为这些看起来像是成员函数的声明。)

如果你使用的是 C++11，你可以这样写

class CChildView : public CWnd
{
    // ...
    BackGround Bg1 {0}; 
    BackGround Bg2 {-WINDOW_HEIGHT};
};

用花括号，或者你可以初始化构造函数的初始化列表中的成员，这适用于所有 C++ 版本:

class CChildView : public CWnd
{
    CChildView();
    // ...
    BackGround Bg1; 
    BackGround Bg2;
};

// ... 

CChildView::CChildView() : Bg1(0), Bg2(-WINDOW_HEIGHT)
{
    // ...
}