c++之多态性动态数组的使用

读林锐博士的<高质量程序设计c/c++>关于数组指针的使用

注意点：

1.多态和指针算术运算不能混合使用，数组操作总会涉及到指针运算，因此多态和数组不应该混合运用

2.不要在数组中直接存放多态对象，而是用基类指针或者基类的智能指针代替。

附上代码：

#include <iostream>
using namespace std;

struct Point{
	Point(int x,int y):m_x(x),m_y(y){}
	int m_x;
	int m_y;
};

ostream& operator<<(ostream &os,const Point& p)
{
	cerr<<"\n{\tHorizontalOrdinate="<<p.m_x\
		<<"\n\tVerticalOrdinate   ="<<p.m_y<<"\n}\n";
	return os;
}

class Shape{
	Point m_origin;

public:
	Shape():m_origin(0,0){}
	explicit Shape(const Point& origin):m_origin(origin){}
	virtual ~Shape(){cerr<<"Shape::~Shape()"<<endl;}

	Point GetOrigin()const{return m_origin;}

	virtual void Draw()const{
		cerr<<"Shape::Draw()"<<endl;

		cerr<<"Origin Point"<<m_origin<<endl;
	}
};

class Circle: public Shape{
	int m_radius;
public:
	Circle():m_radius(1){}
	Circle(const Point&origin,int radius):Shape(origin),m_radius(radius){}

	virtual ~Circle(){cerr<<"Circle::~Circle()"<<endl;}

	int GetRadius()const{return m_radius;}
	virtual void Draw()const{
		cerr<<"Circle::Draw()"<<endl;
		cerr<<"Origin Point:"<<GetOrigin()\
			<<"Radius="<<m_radius<<endl<<endl;
	}
};

class Rectangle:public Shape{
	Point m_rightButtom;//right-bottom point,m_origin as left-top point
public:
	Rectangle():m_rightButtom(1,1){}
	Rectangle(const Point& leftTop,const Point&rightBottom):Shape(leftTop),m_rightButtom(rightBottom){}

	virtual ~Rectangle(){
		cerr<<"Rectangle::~Rectangle()"<<endl;
	}

	Point GetLeftTop()const{return GetOrigin();}
	Point GetRightBottom()const{return m_rightButtom;}

	virtual void Draw()const{
		cerr<<"Rectangle::Draw()"<<endl;
		cerr<<"Left-top point:"<<GetLeftTop()\
			<<"Right-bottom point:"<<m_rightButtom<<endl;
	}

};

void DrawShapes( Shape *shapes[],int numOfShapes){

	for(int i=0;i<numOfShapes;++i){
		shapes[i]->Draw();
	}
}

/*
void DrawShapes(const Shape shapes[],int numOfShapes){
	for (int i=0;i<numOfShapes;++i)
	{
		Shape *p =(Shape*)shapes;
		if(typeid(*p)==typeid(Shape)){
			p->Draw();
			p++;
		}
		
		else if (typeid(*p)==typeid(Circle))
		{
			Circle*q =(Circle*)p;
			q->Draw();
			p=++q;
		}
		else if (typeid(*p)==typeid(Rectangle))
		{
			Rectangle*r =(Rectangle*)p;
			r->Draw();
			p==++r;
		}
		else ;
		
	}
	}
	*/

	int main(){
		Shape *p=new Shape(Point(1,1));
		Circle*q = new Circle(Point(2,2),5);
		Rectangle *r=new Rectangle(Point(3,3),Point(4,4));

		Shape *myShape[3];
		myShape[0] = p;
		myShape[1] = q;
		myShape[2] = r;
		/*
		for (int i =0;i<3;i++)
		{
			myShape[i]->Draw();
		}
		*/
		DrawShapes(myShape,3);

	}

另外如果确实需要使用多态数组，可用STL配合普通指针和智能指针使用。