Friend function wont work due to undeclared identifier

Asked Jun 04 '20 at 11:09

Active Jun 04 '20 at 11:09

Viewed 430 times

This is the Foo.hpp

#ifndef Foo_hpp
#define Foo_hpp

#include <stdio.h>
#include "Bar.hpp"

class Bar;

class Foo
{
private:
   int z;
public:
   void addY(Bar &x);
};
#endif /* Foo_hpp */

This is the Bar.hpp

#ifndef Bar_hpp
#define Bar_hpp

#include <stdio.h>
#include "Foo.hpp"

class Bar
{
private:
    int y;
public:
    friend void Foo::addY(Bar&);//use of undeclared identifier 'Foo'
};
#endif /* Bar_hpp */

I dont even know why it keeps giving me this error, I try to work on it and try to see if I misspell or mistype anything. I even try to rewrite everything form scratch and still come up with the same error.

asked Jun 04 '20 at 11:09

prayoga yoga

2

Remove `#include "Bar.hpp"`. You don't need it. (It looks like you tried to fix a circular dependency with a forward declaration, but that's not enough.) – molbdnilo Jun 04 '20 at 11:11
@molbdnilo wow that actually work, but why thou can you explain it? – prayoga yoga Jun 04 '20 at 11:15
1

Because you got rid of the definition of `Bar`, which would need the definition of `Foo`, wihch doesn't exist at that point. (Remember that `#include "file"` literally only means "insert the contents of 'file' here".) – molbdnilo Jun 04 '20 at 11:17
Unrelated: `#include ` instead of `#include ` – Ted Lyngmo Jun 04 '20 at 11:17
@molbdnilo ma thank you for the help I almost gave up with this thing. – prayoga yoga Jun 04 '20 at 11:24
@TedLyngmo Why thou, is there any significant different of using the instead of ? – prayoga yoga Jun 04 '20 at 11:26
1

@prayogayoga `cstdio` is the c++ equivalent of the c header `stdio.h`. – StefanKssmr Jun 04 '20 at 11:28
2

What @StefanKssmr said - and some implementations actually puts the content in the `std` namespace only - which is nice. – Ted Lyngmo Jun 04 '20 at 11:31
1

@TedLyngmo Oh I see well thank you – prayoga yoga Jun 04 '20 at 11:33

Friend function wont work due to undeclared identifier

0 Answers0