'this'指针，使用'this'指针继承子类中超类的函数
嗨，我想了解如何使用'this'指针。现在我编写了一个示例程序，它使用类Image，它是类BMP的子类。现在，函数TellWidth和TellHeight在BMP类中声明。现在编译器给出了一个错误，表示在Image中不存在TellWidth函数。但由于Image是BMP的子类，因此它不能继承BMP中的函数。
我该如何解决这个问题
void Image :: invertcolors()
{
int x;
int y;
int width =(*this).TellWidth();
int height = (*this)->TellHeight();
for(x=0,x<=height-1;x++){
for(y=0,y<=width-1;y++){
(*this)(x,y)->Red = (255 - (*this)(x,y)->Red);
(*this)(x,y)->Blue = (255 - (*this)(x,y)->Blue);
(*this)(x,y)->Green = (255 - (*this)(x,y)->Green);
}
}
delete width;
delete height;
}
class Image : public BMP
{
public:
void invertcolors();
void flipleft();
void adjustbrightness(int r, int g, int b) ;
};
class BMP {
private:
int Width;
int Height;
public:
int TellBitDepth(void) const;
int TellWidth(void) const;
int TellHeight(void) const;
};
没有找到相关结果
已邀请:
3 个回复
信藉乒
很可能在类中声明为（或没有访问者修饰符）。类需要或才能访问它，如果你想在类中覆盖它，它也必须是。 适当的用法是这样的：阅读获取的快速教程。佩疵瓦
的一点：你很少需要明确提及它。通常的例外是当你需要将它传递给非成员函数时（这里似乎不是这种情况。） 当你在一个类成员函数中时，可以简单地被访问为，而可以被调用为。 以下是对您的代码的一些评论。我希望他们有所帮助。void Image :: invertcolors() { // Don't define these here; that's old C-style code. Declare them where // they're needed (in the loop: for (int x=0...) int x; int y; // Change the lines below to // int width = TellWidth(); // int height = TellHeight(); // (*this).TellWidth() should work, but is redundant; // (*this)->TellHeight() should probably *not* work, as once you've // dereferenced *this, you're dealing with an object instance, not a // pointer. (There are ways to make (*this)->that() do something useful, // but you're probably not trying something like that.) int width =(*this).TellWidth(); int height = (*this)->TellHeight(); for(x=0,x<=height-1;x++){ for(y=0,y<=width-1;y++){ // After locating the BMP class through google (see Edit 2), // I've confirmed that (*this)(x,y) is invoking a (int,int) operator // on the BMP class. It wasn't obvious that this operator // was defined; it would have been helpful if you'd posted // that part of the header file. (*this)(x,y)->Red = (255 - (*this)(x,y)->Red); (*this)(x,y)->Blue = (255 - (*this)(x,y)->Blue); (*this)(x,y)->Green = (255 - (*this)(x,y)->Green); } } // These are int values. They can't be deleted, nor do they need to be. // I'm sure the compiler has told you the same thing, though perhaps not // in the same way. delete width; delete height; }的目的是什么。 编辑2：这是原始BMP类的来源。抚驰
class Image : public BMP { public: void invertcolors(); void flipleft(); void adjustbrightness(int r, int g, int b) ; };