C++: Identifier of class name in same namepace undefined - c++

Question

I have two classes SHCalculator and SphericalLightProbe in separate files. I completely stripped them down to present the error I'm getting so these are the four files:
SHCalculator.h
#pragma once
namespace SphericalHarmonics
{
class SHCalculator
{
private:
public:
void Test();
SphericalLightProbe Test2();
};
}
SHCalculator.cpp
#include "pch.h"
#include "SphericalLightProbe.h"
#include "SHCalculator.h"
namespace SphericalHarmonics
{
void SHCalculator::Test()
{
SphericalLightProbe sp(2, 3.4f);
for (int i = 0; i < sp.coeffs.size(); i++)
{
std::cout << sp.coeffs[i] << std::endl;
}
}
SphericalLightProbe SHCalculator::Test2()
{
SphericalLightProbe sp(2, 4.3f);
for (int i = 0; i < sp.coeffs.size(); i++)
{
std::cout << sp.coeffs[i] << std::endl;
}
return sp;
}
}
SphericalLightProbe.h
#pragma once
namespace SphericalHarmonics
{
class SphericalLightProbe
{
private:
public:
SphericalLightProbe() { }
SphericalLightProbe(int numCoeffs);
SphericalLightProbe(int numCoeffs, float value);
std::vector<Eigen::Vector3f> coeffs;
};
}
SphericalLightProbe.cpp
#include "pch.h"
#include "SphericalLightProbe.h"
namespace SphericalHarmonics
{
SphericalLightProbe::SphericalLightProbe(int numCoeffs)
{
coeffs.resize(numCoeffs);
}
SphericalLightProbe::SphericalLightProbe(int numCoeffs, float value)
{
coeffs.resize(numCoeffs, Eigen::Vector3f(value, value, value));
}
}
This gives me a bunch of errors:
C2238 unexpected token(s) preceding ';'
C2059 syntax error: '('
Message see declaration of 'SphericalHarmonics::SHCalculator'
E0020 identifier "SphericalLightProbe" is undefined
C3646 'Test2': unknown override specifier
C2039 'Test2': is not a member of 'SphericalHarmonics::SHCalculator'
If I remove Test2() by commenting it out, all errors disappear. I'm trying to understand why.

Answer 1

You are missing the includes in your SHCalculator.h header;
Try something like:
#pragma once
#include "SphericalLightProbe.h"
namespace SphericalHarmonics
{
class SHCalculator
{
private:
public:
void Test();
SphericalLightProbe Test2();
};
}
Note that if your SHCalculator.cpp file includes above, the duplicate #include "SphericalLightProbe.h" line is not required.
But if you want to avoid for whatever reason the include, use forward declaration instead, like:
#pragma once
namespace SphericalHarmonics {
class SphericalLightProbe;
// ...
} // namespace SphericalHarmonics
Note that forward declaration normally does not force you to switch to pointers (like SphericalLightProbe *).