Undefined symbols for architecture x86_64

[Nykeriab]

Ob.hpp

#ifndef Ob_hpp
#define Ob_hpp
#include <stdio.h>
class Ob

{

public:

Ob(void);

public:

~Ob(void);

virtual void Show()=0;

};
#endif /* Ob_hpp */

PAIR.hp

#ifndef PAIR_hpp

#define PAIR_hpp

#pragma once

#include <stdio.h>

#include <string>

#include <iostream>

#include "Ob.hpp"

using namespace std;
class PAIR : public Ob

{

public:

PAIR(void);

public:

virtual ~PAIR(void);

void Show();

PAIR(int, int);

PAIR(const PAIR&);
int get_first(){return first;}
int get_second(){return second;}

void set_first(int);
void set_second(int);

PAIR&amp; operator=(const PAIR&amp;);
void operator&gt;(const PAIR&amp;);
void operator&lt;(const PAIR&amp;);
void operator==(const PAIR&amp;);
void operator!=(const PAIR&amp;);

friend istream&amp; operator&gt;&gt;(istream&amp;in, PAIR&amp;c);
friend ostream&amp; operator&lt;&lt;(ostream&amp;out, const PAIR&amp;c);

protected:

int first;

int second;

};

#endif /* PAIR_hpp */

Error:

Undefined symbols for architecture x86_64:

"Ob::Ob()", referenced from:

PAIR::PAIR() in PAIR.o

PAIR::PAIR(int, int) in PAIR.o

PAIR::PAIR(PAIR const&) in PAIR.o

"Ob::~Ob()", referenced from:

PAIR::~PAIR() in PAIR.o

ld: symbol(s) not found for architecture x86_64

clang: error: linker command failed with exit code 1 (use -v to see invocation)

There's such errors in the compilation, if you leave only Class PAIR, that's, "public Ob" to clean up, it's working.

[Duquan]

The contact editor does not see the definition of default designer Ob♪

You announced it.

class Ob
{
public:
    Ob(void);
    //...

but they either forgot to identify or have not connected the project file where the designer is defined.