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Inheritance problem

cidron (12)
Hi all!

I really thought that I understood the aspects of inheritance, but when I run this program: http://pastebin.com/P51bzYdf , so there must be that I did not understand it after all :(. Could anyone please explain?

I end up with some strange linker errors saying:

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1
 
1>Compiling...
1>mainfunc.cpp
1>Linking...
1>mainfunc.obj : error LNK2019: unresolved external symbol "public: class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > __thiscall Shape::toString(void)" (?toString@Shape@@QAE?AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@XZ) referenced in function _main
1>mainfunc.obj : error LNK2019: unresolved external symbol "public: class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > __thiscall Shape::getColor(void)" (?getColor@Shape@@QAE?AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@XZ) referenced in function _main
1>mainfunc.obj : error LNK2019: unresolved external symbol "public: class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > __thiscall Shape::getLine(void)" (?getLine@Shape@@QAE?AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@XZ) referenced in function _main
1>mainfunc.obj : error LNK2019: unresolved external symbol "public: __thiscall Shape::Shape(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >,class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >)" (??0Shape@@QAE@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@0@Z) referenced in function "public: __thiscall Circle::Circle(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >,class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >,double)" (??0Circle@@QAE@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@0N@Z)
1>"path" : fatal error LNK1120: 4 unresolved externals
1>Build log was saved at "..."
1>
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========


Thanks a bunch!

I might as well provide the sourcecode here:

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///////////////////
//shape.h:
///////////////////

#ifndef SHAPE_H
#define SHAPE_H

#include <string>
#include <cmath>
#include "part2.h"

using namespace std;

#define PI 4.0 * atan(1.0) 	//This line enables you to use PI in your calculations

class Shape {
private:
	string color;
	string line;
public:
	//Shape(){}
	Shape(string color, string line);	//Constructor
	void setColor(string color);		//Used to change the color
	void setLine(string line);			//Used to change the line type
	string getColor();				//Returns the color
	string getLine();				//Returns the line type
	string toString();				//Returns a string that descibes the shape in this format "Color = blue, Line = dotted"
}; 

#endif

/*---------------------------*/


///////////////////
//shape.cpp:
///////////////////
#include <string>
#include <sstream>

#include "shape.h"

using namespace std;


Shape::Shape(string color, string line){
	this->color = color;
	this->line = line;
}

void Shape::setColor(string color){
	this->color = color;
}

string Shape::getColor(){
	return color;
}

void Shape::setLine(string line){
	this->line = line;
}

string Shape::getLine(){
	return line;
}

string Shape::toString(){
	stringstream ss;
	ss << "Color = " << color << ", Line = " << line;
	return ss.str();
}

/*---------------------------*/


///////////////////
//part2.h:
///////////////////

#include "shape.h"

using namespace std;

class Circle : public Shape
{
private:
	double radius;
public:
	//Circle() : Shape(){ }
	Circle(string color, string line, double radius) : Shape(color, line)	, radius(radius) { }
	void setRadius(double radius)
	{
		if(radius<0) 
			this->radius=0; 
		else 
			this->radius=radius;
	}
	double getRadius(){return radius;}
	double getCirc(){return 2*PI*radius;}
	double getArea(){return radius*radius*PI;}
};

/*---------------------------*/


///////////////////
//mainfunc.cpp:
///////////////////

#include "part1.h"
#include "shape.h"
#include "part2.h"
#include <iostream>
#include <string>

using namespace std;
	
int main()
{
	// Inheritance problem

	//Circle rund("red", "dotted", 2);
	Circle* rund = new Circle("red", "dotted", 2);
	
	cout << "\nFeatures of the circle using the Circle object's get-funcs:" << endl;
	cout << "Color: " << rund->getColor() << ", Line: " << rund->getLine();
	cout << ", Radius: " << rund->getRadius() << endl;
	cout << "Features of the circle using the Shape class' toString-func:" << endl;
	cout << rund->toString() << endl;

	delete rund;

	return 0;
}
m4ster r0shi (2201)
You probably haven't put all the files in the project. (You missed shape.cpp). But you can actually do it in one file. Just copy-paste this here in your compiler and remove any line writing:

#include "part1.h" or
#include "part2.h" or
#include "shape.h"

It worked for me.
cidron (12)
Thanks!
It turns out that the code was right, but I had messed up the #include's. It worked when I sat up the #indef-#endif-thingy. Has anyone a general rule to follow when one is including stuff?
firedraco (6243)
If you need to use stuff inside of it, you will need to include it. If you just need a pointer or reference (for example when writing a class), then you just need to forward declare it.

Look here for more info: http://www.cplusplus.com/forum/articles/10627/
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