Unresolved external symbol error in C++. Creating an object from other object's method

Question

I am still learning C++, so reading all similar posts (on SO) about this problem did not give me clarity.

I want to create a method called getFixedLeg inside an object SwapFixedIborDefinition that will return AnnuityCouponFixedDefinition object.

While trying to solve the problem I found that in the Debug folder of the Project these objects where created:

main.obj
SwapFixedIborDefinition.obj
GeneratorSwapFixedIbor.obj

If I comment out the method and all the mentioning of the AnnuityCouponFixedDefinition class then everything works fine.

I have 2 questions:

1. How to locate and resolve the error I have?
2. Why do I have different errors when I launch my project (I work in VS2017) in Debug and Release modes?

In case of Debug I get:

    Error   LNK2019 unresolved external symbol "public: __thiscall AnnuityCouponFixedDefinition::AnnuityCouponFixedDefinition(double,class GeneratorSwapFixedIbor,double)" (??0AnnuityCouponFixedDefinition@@QAE@NVGeneratorSwapFixedIbor@@N@Z) referenced in function "public: class AnnuityCouponFixedDefinition __thiscall SwapFixedIborDefinition::getFixedLeg(double,class GeneratorSwapFixedIbor,double)" (?getFixedLeg@SwapFixedIborDefinition@@QAE?AVAnnuityCouponFixedDefinition@@NVGeneratorSwapFixedIbor@@N@Z)   ProjectGenchoCurveConstruction  C:\Users\yanto\source\repos\ProjectGenchoCurveConstruction\ProjectGenchoCurveConstruction\SwapFixedIborDefinition.obj   1   

and

    Error   LNK1120 1 unresolved externals  ProjectGenchoCurveConstruction  C:\QuantLib-1.11\Debug\ProjectGenchoCurveConstruction.exe   1   

while for Release mode I get:

    Error   LNK1104 cannot open file 'deffile'  ProjectGenchoCurveConstruction  C:\Users\yanto\source\repos\ProjectGenchoCurveConstruction\ProjectGenchoCurveConstruction\LINK  1   

all my code is 3 classes and main file, i.e. 7 files:

main.cpp

#include <iostream>
#include <memory>
#include "GeneratorSwapFixedIbor.h"
#include "SwapFixedIborDefinition.h"
// #include "AnnuityCouponFixedDefinition.h"
int main()
{
    GeneratorSwapFixedIbor generator;
    double etc = 0;
    double mktQuote = 0;

    //SwapFixedIborDefinition mySwap(mktQuote, generator, etc);
    std::cout << " finish";

    return 0; 
}

GeneratorSwapFixedIbor.h

#pragma once
class GeneratorSwapFixedIbor
{
    double somePrimitive;
    double startDate;
    double endDate;
    double notional;
    double rate;
    int zero;
public:
    GeneratorSwapFixedIbor();
    ~GeneratorSwapFixedIbor();
    double getSomePrimitive();

};

GeneratorSwapFixedIbor.cpp

#include "GeneratorSwapFixedIbor.h"
#include <iostream>

GeneratorSwapFixedIbor::GeneratorSwapFixedIbor()
    //: somePrimitive{ somePrimitive }
{
    somePrimitive = 101;
    std::cout << "Object GeneratorSwapFixedIbor is being created" << somePrimitive;
}

GeneratorSwapFixedIbor::~GeneratorSwapFixedIbor(){}

double GeneratorSwapFixedIbor::getSomePrimitive()
{
    return somePrimitive;
}

AnnuityCouponFixedDefinition.h

#pragma once
#include "GeneratorSwapFixedIbor.h"
#include "AnnuityCouponFixedDefinition.h"


class AnnuityCouponFixedDefinition
{
//private:
    GeneratorSwapFixedIbor generator;
    double mktQuote;
    double etc;
public:
    AnnuityCouponFixedDefinition();
    AnnuityCouponFixedDefinition(double mktQuote, GeneratorSwapFixedIbor generator, double etc);
    ~AnnuityCouponFixedDefinition();
};

AnnuityCouponFixedDefinition.cpp

#include <iostream>
#include "SwapFixedIborDefinition.h"
#include "GeneratorSwapFixedIbor.h"
#include "AnnuityCouponFixedDefinition.h"

AnnuityCouponFixedDefinition::AnnuityCouponFixedDefinition()
{
    std::cout << "Object AnnuityCouponFixedDefinition is being created";
}

AnnuityCouponFixedDefinition::AnnuityCouponFixedDefinition(double mktQuote, GeneratorSwapFixedIbor generator, double etc)
{
    std::cout << "Object AnnuityCouponFixedDefinition is being created";
}

AnnuityCouponFixedDefinition::~AnnuityCouponFixedDefinition(){}

SwapFixedIborDefinition.h

#pragma once
#include "GeneratorSwapFixedIbor.h"
#include "AnnuityCouponFixedDefinition.h"

class SwapFixedIborDefinition
{
//private:
    GeneratorSwapFixedIbor generator;
    double mktQuote;
    double etc;

public:
    SwapFixedIborDefinition();
    SwapFixedIborDefinition(double mktQuote, GeneratorSwapFixedIbor generator, double etc);
    AnnuityCouponFixedDefinition getFixedLeg(double mktQuote, GeneratorSwapFixedIbor generator, double etc);
    ~SwapFixedIborDefinition();
    double get_smth();
};

SwapFixedIborDefinition.cpp

#include <iostream>
#include "SwapFixedIborDefinition.h"
#include "GeneratorSwapFixedIbor.h"
#include "AnnuityCouponFixedDefinition.h"


SwapFixedIborDefinition::SwapFixedIborDefinition() {}

SwapFixedIborDefinition::SwapFixedIborDefinition(double mktQuote, GeneratorSwapFixedIbor generator, double etc)
    : mktQuote{ mktQuote }, generator{ generator }, etc{ etc }
{
    std::cout << "Object SwapFixedIbor is being created";
}

AnnuityCouponFixedDefinition SwapFixedIborDefinition::getFixedLeg(double mktQuote, GeneratorSwapFixedIbor generator, double etc)
{
    return AnnuityCouponFixedDefinition(mktQuote, generator, etc);
}

double SwapFixedIborDefinition::get_smth() {
    std::cout << " we can call smth ";
    return 100;
}

SwapFixedIborDefinition::~SwapFixedIborDefinition(){}

This is how my solution explorer looks like.