Undefined Reference

Question

I am learning about classes in c++, so I am writing the following simple code in separate files and while vscode is not showing any problems, the compiler is giving me an error when compiling.

main.cpp

#include <iostream>
#include "constants.h"
#include "cylinder.h"

int main ()
{
    Cylinder cylinder1(10,10);

    Cylinder cylinder2;

    std::cout << "volume : " << cylinder1.volume() << std::endl;

    return 0;
}

cylinder.h

#ifndef CYLINDER_H
#define CYLINDER_H
#include "constants.h"

class Cylinder {
    
    public:

    Cylinder () = default;

    Cylinder (double rad_param, double height_param);

    double volume () { return PI * base_radius * base_radius * height; }

    double get_base_radius () { return base_radius; }
    double get_height () { return height; }
    void set_base_radius (double rad_param) {base_radius = rad_param; }
    void set_height (double height_param) {height = height_param; }

    private:

    double base_radius {1};
    double height {1};
};

#endif

cylinder.cpp

#include "cylinder.h"

Cylinder::Cylinder (double rad_param, double height_param)
    {
        base_radius = rad_param;
        height = height_param;
    }

constants.h

#ifndef CONSTANTS_H
#define CONSTANTS_H

const double PI {3.1415926535897932384626433832795};

#endif

When I try to compile, I get this error:

Starting build... C:\mingw64\bin\g++.exe -fdiagnostics-color=always -g -std=c++23 "C:\PCHDD\Programming PCHDD\Learning\Template\main.cpp" -o "C:\PCHDD\Programming PCHDD\Learning\Template\main.exe" C:/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/13.2.0/../../../../x86_64-w64-mingw32/bin/ld.exe: C:\Users\90539\AppData\Local\Temp\cc6YTSXM.o: in function main': C:/PCHDD/Programming PCHDD/Learning/Template/main.cpp:9:(.text+0x30): undefined reference to Cylinder::Cylinder(double, double)' collect2.exe: error: ld returned 1 exit status

Build finished with error(s).

The terminal process terminated with exit code: -1. Terminal will be reused by tasks, press any key to close it.

I did some search and found that it may be a linker error caused by not implementing a function, but all functions are implemented in the main.cpp ! I don't know what I'm doing wrong.

Thanks in advance for your help.