Linker Error "unresolved external symbol" when using constructor of other class - c++

Question

I've been struggling to find why my linker gets an unresolved external symbol error. The error looks like this:
Error
LNK2019
unresolved external symbol "public: __thiscall Shader::Shader(char const *)" (??0Shader##QAE#PBD#Z) referenced in function "public: __thiscall GridWorldGPGPU::GridWorldGPGPU(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >,unsigned int)" (??0GridWorldGPGPU##QAE#V?$basic_string#DU?$char_traits#D#std##V?$allocator#D#2##std##I#Z)
DV2556_Project
grid_world_GPGPU.obj
1
As far as I understand it it has something to do with that my linker finds the declaration of the Shader::Shader(char const *)-function but cannot find the definition. I have been staring at this for hours and cannot figure out why the linker becomes sad.
grid_world_GPGPU.h:
#ifndef GRID_WORLD_GPGPU_H
#define GRID_WORLD_GPGPU_H
#include "grid_world.h"
#include <../swift_open_gl.h>
class GridWorldGPGPU : public GridWorld {
private:
Shader* compute_shader_ = nullptr;
public:
GridWorldGPGPU(std::string in_path_shader, unsigned int in_side = 1);
};
#endif // !GRID_WORLD_GPGPU_H
grid_world_GPGPU.cpp:
GridWorldGPGPU::GridWorldGPGPU(std::string in_path_shader, unsigned int in_side)
: GridWorld(in_side) {
this->compute_shader_ = new Shader(in_path_shader.c_str());
}
The Shader-class is defined in the swift_open_gl.h file:
#ifndef SWIFT_OPEN_GL_H
#define SWIFT_OPEN_GL_H
#include <glad/glad.h>
#include <GLFW/glfw3.h>
class Shader {
public:
Shader(const char* cs_path);
};
#endif // !SWIFT_OPEN_GL_H
And swift_open_gl.cpp has this:
#include "..\swift_open_gl.h"
inline Shader::Shader(const char * cs_path) {
//Do stuff
}
I've tried with and without the inline (Visual Studio added it when I tried moving the function definition between the .h-file and a .cpp-file, so I decided to try it) and i have verified that the #include <../swift_open_gl.h> doesn't occur anywhere else in the project than the files listed above.
An extra set of eyes to look over this would be appreciated!

Answer 1

Provide default constructor of the class as well.
class Shader {
public:
Shader(){} // default constructor
Shader(const char* cs_path);
};
Dont use inline in Shader::Shader(const char* cs_path){} definition