Error using object from different class

Question

Foo.h

class Foo{
private:
    void printSpecialBar(Bar b);//syntax error: Identifier Bar

Foo.cpp

#include "Bar.h"

void Foo::printSpecialBar(Bar b)
{
    //code goes here
}

Bar has the default constructor and one that takes two int's.

What is the problem with the syntax error? I tried using the scope resuloution operator Bar::Bar b but it didn't fix it.

Since you are using Bar inside one of Foo's member function declarations, you must tell the compiler what it is. Otherwise, the compiler thinks that you made a typo. Forward-declaring Bar with class Bar; would give compiler enough information to compile your program, as long as the declaration precedes the point where Bar is first used. — Sergey Kalinichenko
– Sergey Kalinichenko, Commented Jan 28, 2014 at 3:22
@awesomeyi Can certainly include it, and it would fix the problem. However, it is not strictly required here: a forward declaration would be enough. — Sergey Kalinichenko
– Sergey Kalinichenko, Commented Jan 28, 2014 at 3:26
@awesomeyi and where possible, a forward declaration is always preferred to including the full type definition. Generating chains of .h files can substantially increase compile times and sometimes lead to errors. — Darinth
– Darinth, Commented Jan 28, 2014 at 4:21

He Shiming · Accepted Answer · 2014-01-28 03:17:40Z

1

A typical practice would be to put

class Bar;

in Foo.h, before any reference to Bar class, and include the actual class like

#include "Bar.h"

in Foo.cpp.

answered Jan 28, 2014 at 3:17

He Shiming

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1 Comment

Well it really has nothing to do with #pragma once. So either position would be okay.

Tyler Gaona · Accepted Answer · 2014-01-28 03:19:02Z

0

Since Foo.h references Bar, either use a forward declaration or #include "Bar.h" in Foo.h

answered Jan 28, 2014 at 3:19

Tyler Gaona

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