c++ - It is said abstract class for a virtual function that is implemented. It works with three of four similar implementations -
it seems problem circle.cpp if code looks same in point.cpp. i've been looking @ code long time , haven't found different in 2 files. here error message:
>------ build started: project: ou5, configuration: release win32 ------ 1> circle.cpp 1> ou5.cpp 1>c:\users\jonas\documents\visual studio 2010\projects\ou5\ou5\shapeptr.h(52): error c2259: 'shape' : cannot instantiate abstract class 1> due following members: 1> 'shape *shape::clone(void) const' : abstract 1> c:\users\jonas\documents\visual studio 2010\projects\ou5\ou5\shape.h(21) : see declaration of 'shape::clone' 1>ou5.cpp(20): error c2259: 'shape' : cannot instantiate abstract class 1> due following members: 1> 'shape *shape::clone(void) const' : abstract 1> c:\users\jonas\documents\visual studio 2010\projects\ou5\ou5\shape.h(21) : see declaration of 'shape::clone' 1>ou5.cpp(27): error c2259: 'shape' : cannot instantiate abstract class 1> due following members: 1> 'shape *shape::clone(void) const' : abstract 1> c:\users\jonas\documents\visual studio 2010\projects\ou5\ou5\shape.h(21) : see declaration of 'shape::clone' 1> point.cpp 1> polygon.cpp 1> rectangle.cpp ========== build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ========== the code base class pure virtual function:
#ifndef shape_h #define shape_h using namespace std; #include <iostream> #include <ostream> class shape { public: shape() { cout << "shape constructor" << endl; } shape(double xval, double yval) { x = xval; y = yval; } virtual shape* clone() const = 0; virtual double area() { return 1; } virtual void print() const{} virtual ostream& printf(ostream &os){return os;} /* // copy constructor shape(const shape *sp) { // copy string our newly allocated memory sp =this->clone(); }*/ /*shape & operator=(const shape & sptr) { if(this!= &sptr) { *this = sptr.clone(); } return *this; }*/ double getx() const { return x; } double gety() const { return y; } virtual ~shape() {cout << "shape raderas av destruktor" <<endl; } protected: double x; //attribut double y; //attribut shape *sp; }; #endif point.h working:
#ifndef point_h #define point_h #include "shape.h" using namespace std; #include <iostream> #include <fstream> class point : public shape { public: point() { cout << "point constructor" << endl; } point(double x, double y, double sz) : shape(x,y), size(sz) { cout << "point constructor" << endl; } void las(istream &is) { >> x >> y >> size; } ostream& printf(ostream &os) ; void print() const; double area(); shape* clone() const; virtual ~point(){cout << "point raderas av destruktor" << endl;} private: double size; //attribut }; #endif point.cpp:
#include "point.h" #include <ostream> using namespace std; shape* point::clone() const { return new point( *this); } void point::print() const { cout << "point: "; cout <<"(" << this->x<<"," << this->y << ")" << this->size << endl; } ostream& point::printf(ostream &os) { os << "point: "; os <<"(" << this->x<<"," << this->y << ")" << this->size << endl; return os; } double point::area() { return size; } the files problem. first circle.h:
#ifndef circle_h #define circle_h #include "shape.h" using namespace std; #define m_pi 3.141592654 #include <fstream> #include <iostream> class circle : public shape { public: circle() { cout << "circle constructor" << endl; } circle(double x, double y, double rad) : shape(x,y), radie(rad) { cout << "circle constructor" << endl; } void las(istream &is) { >> x >> y >> radie; } ostream& printf(ostream &os); double area(); void print() const; shape* clone() const; virtual ~circle(){cout << "circle raderas av destruktor" << endl;} private: double radie; //attribut }; #endif then circle.cpp:
#include "circle.h" using namespace std; #include <ostream> shape* circle::clone() const {return new circle( *this);} double circle::area() { double tmparea; tmparea = m_pi * radie * radie; return tmparea; } void circle::print() const { cout << "circle: "; cout <<"(" << this->x<<"," << this->y << ")" << this->radie << endl; } ostream& circle::printf(ostream &os) { os << "circle: "; os <<"(" << this->x<<"," << this->y << ")" << this->radie << endl; return os; } the problem clone , looks same in file working , not working file. working file point.cpp works 2 other files not posted here.
i add shapeptr.h here:
#ifndef shapeptr_h #define shapeptr_h #include "shape.h" #include "circle.h" #include "point.h" #include "polygon.h" #include "rectangle.h" #include <ostream> #include <istream> #include <vector> #include <fstream> #include <string> using namespace std; class shapeptr { public: shapeptr() { sptr = 0; numshapes = numshapes + 1; } shapeptr(shape * v)//: shape(v->getx(),v->gety()) { sptr = v; numshapes = numshapes + 1; } // copy constructor shapeptr(const shape &sp) { // copy string our newly allocated memory sptr = sp.clone(); } const shapeptr & shapeptr::operator=(const shape & sp) { if(this->sptr!= &sp) { sptr = sp.clone(); } return *this; } ~shapeptr(){ numshapes = numshapes - 1; cout << "shapeptr raderas av destruktor" << endl; } shape getshape() { return *sptr; } private: shape *sptr; public: static int numshapes; friend istream& operator>>(istream &is, shapeptr & sp); friend ostream& operator<<(ostream &os, const shapeptr & sp); }; int shapeptr::numshapes = 0; ostream& operator<<(ostream &os, const shapeptr & sp) { os << sp.sptr->printf(os); return os; } istream& operator>>(istream &is, shapeptr & sp) { string check; while(!is.eof()) { >> check; if(check == "circle") { circle cir; cir.las( ); sp = shapeptr(new circle(cir)); return is; } if(check == "polygon") { polygon pol; pol.las( ); sp = shapeptr(new polygon(pol)); return is; } if(check == "point") { point poi; poi.las( ); sp = shapeptr(new point(poi)); return is; } if(check == "rectangle") { rectangle rec; rec.las( ); sp = shapeptr(new rectangle(rec)); return is; } } } #endif
based on comments attempting make instance of abstract class in shapeptr.h not valid. point attempt create instance here:
shape getshape() { return *sptr; } as mark b. pointed out fix change return type shape&.
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