一个propety pattern的例子

#include <iostream>using std::cout;using std::cin;using std::endl;#include <vector>using std::vector;#include <cassert>#include <conio.h>enum imageType{LSAT, SPOT};class Image{protected:Image();virtual ~Image();Image( const Image& rhs);Image& operator = (const Image & rhs);public:virtual void PrintInfo() const =0;static Image *findAndClone(imageType);public:virtual imageType returnType() const = 0;virtual Image *clone() const = 0 ;// As each subclass of Image is declared, it registers its prototypestatic void addPrototype(Image *image){assert(image);_prototypes.push_back(image);}private:// addPrototype() saves each registered prototype herestatic vector<Image*>_prototypes;static int _nextSlot;};vector<Image*> Image::_prototypes;int Image::_nextSlot;Image::Image(){}Image::~Image(){}Image::Image(const Image& rhs){}// Client calls this public static member function when it needs an instance// of an Image subclassImage *Image::findAndClone(imageType type){for(int i = 0; i <_prototypes.size(); i++){if(_prototypes[i]->returnType() == type ){return _prototypes[i]->clone();}}}class LandSatImage: public Image{public:LandSatImage();~LandSatImage();protected:LandSatImage( int nDumy);LandSatImage(const LandSatImage& rhs);LandSatImage& operator = (const LandSatImage& rhs);public:virtual Image* clone() const;private:static int id;static LandSatImage _landSatImage;public:imageType returnType() const{return LSAT;}void PrintInfo() const{_tprintf(_T("LandSatImate: %d\r\n"), id);}};int LandSatImage::id =0;LandSatImage LandSatImage::_landSatImage(1);LandSatImage::LandSatImage(){}LandSatImage::~LandSatImage(){}LandSatImage::LandSatImage(int nDumy){addPrototype(this);}LandSatImage::LandSatImage(const LandSatImage& rhs){id++;}Image* LandSatImage::clone() const{return new LandSatImage(*this);}class SpotImage:public Image{public:SpotImage();~SpotImage();protected:SpotImage(int nDumy);SpotImage(const SpotImage& rhs);SpotImage& operator = (const SpotImage& rhs);public:virtual Image* clone() const;private:static int id;static SpotImage _spotImage;public:imageType returnType() const{return SPOT;}void PrintInfo() const{_tprintf(_T("SpotImage: %d\r\n"), id);}};int  SpotImage::id = 0;SpotImage SpotImage::_spotImage(1);SpotImage::SpotImage(){}SpotImage::~SpotImage(){}SpotImage::SpotImage(int nDumy){addPrototype(this);}SpotImage::SpotImage(const SpotImage& rhs){id++;}Image* SpotImage::clone() const{return new SpotImage(*this);}// Simulated stream of creation requestsstatic const int NUM_IMAGES = 8;imageType input[NUM_IMAGES] = {LSAT, LSAT, LSAT, SPOT, LSAT, SPOT, SPOT, LSAT};int main(){Image* imageArray[NUM_IMAGES]={NULL};//cloneint i;for(i = 0; i< NUM_IMAGES; i++){imageArray[i] = Image::findAndClone(input[i]);if(imageArray[i]){imageArray[i]->PrintInfo();}}getch();return 0;}