Class implementation in multiple files

Question

I am trying to implement a class in different cpp files. I understand it is a legitimate thing to do in C++ if the member functions are independent. However one of the member function uses another member function such as in this case:

In function1.cpp

#include "myclass.h"
void myclass::function1()
{ 
    function2();
}

In function2.cpp

#include "myclass.h"
void myclass::function2()
{
....
}

I will get an error of undefined reference to function2. It doesn't work by adding this pointer either. Do I need to declare it in some way in function1.cpp? Thanks~

The header file includes declaration of both functions. It works when function1 and function 2 are in the same file but not when I separate them. I also believe I've added both cpp in the project. I am using Qt creater btw.

have you declared both function1() and function2() in myclass.h? — nobody
– nobody, Commented Aug 4, 2011 at 10:38
You need to have the function declarations of both the functions in the header file (myclass.h). — Sujoy
– Sujoy, Commented Aug 4, 2011 at 10:38
Can you add your myclass.h file? Maybe some error with class declaration - because of those situation is ok, and error mustn't be here — Olympian
– Olympian, Commented Aug 4, 2011 at 10:39
Are you sure that both of the .cpp files are included in your compilation? — sarat
– sarat, Commented Aug 4, 2011 at 10:43
There is no problem with your approach. What's the actual compiler error? — Jan Hudec
– Jan Hudec, Commented Aug 4, 2011 at 11:25

Przemek M · Accepted Answer · 2015-06-19 16:33:28Z

16

As long as myclass.h contains the definition of the class with the declarations of the member functions, you should be fine. Example:

//MyClass.h
#ifndef XXXXXXXX
#define XXXXXXXX
class MyClass
{
  public:
   void f1();
   void f2();
};
#endif

//MyClass1.cpp
#include "MyClass.h"
void MyClass::f1()
{
};

//MyClass2.cpp
#include "MyClass.h"
void MyClass::f2()
{
     f1(); //OK
}

edited Jun 19, 2015 at 16:33

Przemek M

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answered Aug 4, 2011 at 10:38

Armen Tsirunyan

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2 Comments

Bill Over a year ago

hi thanks. I believe this is what I did. Still won't compile though. It works fine when the two functions are in the same file. I am working with Qt and both files are listed in the project.

hobbydev Over a year ago

this is not working.

Luchian Grigore · Accepted Answer · 2011-08-04 10:40:13Z

2

This should work. If you get a linker error, make sure you compile both your cpp files, that's what's most probably causing your error.

answered Aug 4, 2011 at 10:40

Luchian Grigore

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Comments

n0rmzzz · Accepted Answer · 2011-08-04 11:18:22Z

1

Everything seems fine to me. There might be something wrong with your build process. You should compile the two .cpp files (using -c option) into object files and link them together in the next stage.

answered Aug 4, 2011 at 11:18

n0rmzzz

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