Declaring Class function error?

Hi all, :)

I am experiencing a strange problem when declaring classes outside the main source file in VC++. I have made an experiment that demonstrates my problem. There are two files: “main.cpp” and “class.cpp”.

“main.cpp” content:

Code:

---

#include "class.cpp"

int main() {
        return 0;
}

---

“class.cpp” content:

Code:

---

class Class {
public:
        void Test();
};

void Class::Test() {
        return;
}

---

When I try to compile I get following error:

--------------------Configuration: main - Win32 Debug--------------------
Compiling...
main.cpp
class.cpp
Linking...
class.obj : error LNK2005: "public: void __thiscall Class::Test(void)" (?Test@Class@@QAEXXZ) already defined in main.obj
Debug/main.exe : fatal error LNK1169: one or more multiply defined symbols found
Error executing link.exe.

main.exe - 2 error(s), 0 warning(s)

It says that the function void Test() is already declared, but how? Please help me, am I doing something wrong? :(

You have to make class.cpp a header file (class.h)...

and in the second part, I think(I'm not sure) it should be

Code:

---

void test::class()
{
    stuff;
}

---

Use inclusion guards around your class declaration too.

Code:

---

#ifndef MY_CLASS_H
#define MY_CLASS_H

class my_class { ...  };

#endif

---

Hey thanks that helpt (renaming to class.h), thanks :)

Thanks for the tip, Zach. I will keep that in mind :)

Usually the bodies of the functions of a class are not placed in a headerfile, but in a sourcefile. So you should have your class definition in a file class.h and its implementation in a file class.cpp. Include the headerfile in both sourcefiles.

You'll also need constructors because you don't have any.

Then changing the file class.h doesn't really change any thing hell it could be a .c file and you r code wouldn't work

In the absence of any explicitly defined constructors, the compiler will provide a do-nothing default constructor (which takes no arguments), and a copy constructor (which makes a shallow copy of your class).

Also, there is one exception to what Shiro said. Templated classes often have to be defined in the same file they are declared (usually a header file). The reason is that many compilers (not all, but many) will choke if they are in separate files.