无法解析的外部符号-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 :)

Answer 1

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);
}

Answer 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);
}

Answer 3

In your definition, you forgot MyClass::

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