Unresolved external symbol - C++

Question

I tried to start to code in C++ after a long time.
I started a little project and got an error after little time :(

I have two classes: MyClass and OtherClass (just as an example)

My main.cpp:

#include "MyClass.h"
#include "OtherClass.h"

int main(){
    OtherClass* otherClass = MyClass::doSomething();

    return 0;
}

OtherClass.h:

#pragma once
class OtherClass
{
public:
OtherClass(int a, int b, int c);
~OtherClass();

private:
    int a, b, c;
};

OtherClass.cpp:

#include "OtherClass.h"

OtherClass::OtherClass(int a, int b, int c)
{
    this->a = a;
    this->b = b;
    this->c = c;
}

OtherClass::~OtherClass(){}

MyClass.h:

#pragma once
#include "OtherClass.h"

class MyClass
{
public:
    static OtherClass* doSomething();

private:
    MyClass();
    ~MyClass();
};

MyClass.cpp:

#include "MyClass.h"

MyClass::MyClass(){}
MyClass::~MyClass(){}

OtherClass* doSomething(){
    return new OtherClass(0, 0, 0);
}

For me everything seems fine.
I'm used to code in C# so maybe I'm missing something important (I guess because I'm getting this error).

The error I get:

Error   1   error LNK2019: Unresolved external symbol ""public: static class OtherClass * __cdecl MyClass::doSomething(void)" (?doSomething@MyClass@@SAPAVOtherClass@@XZ)" in function "_main". D:\Projects\TestProject\main.obj    TestProject

Hope you can help me :)

janm · Accepted Answer · 2013-11-20 00:45:49Z

4

In MyClass.cpp, the function:

OtherClass* doSomething(){
    return new OtherClass(0, 0, 0);
}

Should be qualified with a class name:

OtherClass* MyClass::doSomething(){
    return new OtherClass(0, 0, 0);
}

answered Nov 20, 2013 at 0:45

janm

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1 Comment

TorbenJ Over a year ago

Oh no. I always read OtherClass* MyClass::doSomething() and had this signature in my mind but I haven't written it to "paper" :D Hate these situations. Thanks :) I'll choose this answer as soon as the system lets me do it :) First come, first served. Thanks to the other posters, too :)

BenMorel · Accepted Answer · 2013-12-07 16:48:56Z

2

Your problem is the definition of doSomething(): you defined a global function rather than a member function:

OtherClass* doSomething(){
    return new OtherClass(0, 0, 0);
}

You meant to write

OtherClass* MyClass::doSomething(){
    return new OtherClass(0, 0, 0);
}

edited Dec 7, 2013 at 16:48

BenMorel

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answered Nov 20, 2013 at 0:46

Dietmar Kühl

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Comments

lolando · Accepted Answer · 2013-11-20 00:46:38Z

1

In your definition, you forgot MyClass::

OtherClass* MyClass::doSomething(){
    return new OtherClass(0, 0, 0);
}

answered Nov 20, 2013 at 0:46

lolando

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