C++ RTTI行为未按预期出现
我在MS Visual Studio Express 2012中编写了此代码,以查看rtti行为。C++ RTTI行为未按预期出现,c++,rtti,C++,Rtti,我在MS Visual Studio Express 2012中编写了此代码,以查看rtti行为。 但它没有按预期工作。 我的代码有什么问题 Shape.h class Shape { public: Shape(){} virtual ~Shape(){} virtual double area() = 0; }; class Square : public Shape { int a; public: ~Square(){} Square(i
但它没有按预期工作。
我的代码有什么问题 Shape.h
class Shape
{
public:
Shape(){}
virtual ~Shape(){}
virtual double area() = 0;
};
class Square : public Shape
{
int a;
public:
~Square(){}
Square(int );
virtual double area();
};
class Rectangle : public Shape
{
int l;
int b;
public:
~Rectangle(){}
Rectangle(int,int);
virtual double area();
};
class Circle : public Shape
{
int r;
public:
~Circle(){}
Circle(int);
virtual double area();
};
int main()
{
Shape* c = new Circle(4);
cout<< "Area of circle:" << c->area() << endl;
cout << typeid(c).name();
Shape* s = new Square(4);
cout<< "Area of square:" << s->area() << endl;
cout << typeid(s).name();
Shape* r = new Rectangle(4,5);
cout<< "Area of rectangle:" << r->area() << endl;
cout << typeid(r).name();
}
Area of circle:50.24
class Shape * //Expected class Circle*
Area of square:16
class Shape * //Expected class Square*
Area of rectangle:20
class Shape * //Expected class Rectangle*
ShapeMain.cpp
class Shape
{
public:
Shape(){}
virtual ~Shape(){}
virtual double area() = 0;
};
class Square : public Shape
{
int a;
public:
~Square(){}
Square(int );
virtual double area();
};
class Rectangle : public Shape
{
int l;
int b;
public:
~Rectangle(){}
Rectangle(int,int);
virtual double area();
};
class Circle : public Shape
{
int r;
public:
~Circle(){}
Circle(int);
virtual double area();
};
int main()
{
Shape* c = new Circle(4);
cout<< "Area of circle:" << c->area() << endl;
cout << typeid(c).name();
Shape* s = new Square(4);
cout<< "Area of square:" << s->area() << endl;
cout << typeid(s).name();
Shape* r = new Rectangle(4,5);
cout<< "Area of rectangle:" << r->area() << endl;
cout << typeid(r).name();
}
Area of circle:50.24
class Shape * //Expected class Circle*
Area of square:16
class Shape * //Expected class Square*
Area of rectangle:20
class Shape * //Expected class Rectangle*
typeid()
仅当传递多态类型的左值时才实际执行RTTI查找Shape
是一种多态类型,但您传递的不是Shape
lvalue,而是Shape*
。因此,当您将c
、s
和r
传递到typeid()
时,它会报告这些表达式的静态类型,即Shape*
要获得运行时查找,您可以取消对指针的引用:std::cout