Need help with a Lnk2019 error in an SFML/C++ project

[TankRockett]

I'm currently making a 2D video game using the SFML library on Visual Studio 2019 community with the help of a Youtube tutorial series by Suraj Sharma:

https://www.youtube.com/watch?v=IdKZpv6 xqdw&list=PL6xS OsbVA1ebkU66okp i-KViAO8_9DJKg&in dex=1

Recently i'm making a drop list of buttons to be implemented in the game menu's settings(Video 44 to 48)

For example,when i click on the menu's 'Settings' button the menu will switch into a 'Settings' state that comprises a drop list of resolution options for me to choose from.

Here's the code:

Gui.h

#pragma once
#ifndef GUI_H
#define GUI_H

#include "pch.h"

enum BStates { IDLE = 0,HOVER,ACTIVE };

namespace gui {
	class Button
	{
	private:
		short unsigned bStates;
		short unsigned Id;

		sf::RectangleShape Shape;
		sf::Font* Font;
		sf::Text Text;

		sf::Color TextIdl;
		sf::Color TextHover;
		sf::Color TextActive;

		sf::Color Idle;
		sf::Color Hover;
		sf::Color Active;

		sf::Color OutlIdle;
		sf::Color OutlHover;
		sf::Color OutlActive;
	public:
		Button(float x, float y, float w, float h,
			sf::Font* Font, std::string Text,
			unsigned CharSize, sf::Color TextIdl, sf::Color TextHover, sf::Color TextActive,
			sf::Color Idle, sf::Color Hover, sf::Color Active
			,sf::Color OutlIdle, //= sf::Color::Transparent
		        ,sf::Color OutlHover = sf::Color::Transparent, 
			sf::Color OutlActive = sf::Color::Transparent,
			short unsigned Id = 0);
		~Button();

		//Access
		const bool Pressed()const;
		const std::string GetText()const;
		const short unsigned& GetId()const;
		//Modifier
		void SetText(const std::string Text);
		void SetId(const short unsigned Id);
		//Function
		void Update(const sf::Vector2f& MousePos);
		void Render(sf::RenderTarget& target);
	};
	class DrpList {
	private:
		float Keytime;
		float KeytimeMax;
		sf::Font& Fnt;
		gui::Button* ActivElmnt;
		std::vector<gui::Button*> List;
		bool ShowList;
	public:
		DrpList(float x, float y, float w, float h, sf::Font& Fnt, std::string List[], unsigned NumElemnt, unsigned DefIndex = 0);
		~DrpList();

		//Funcs
		const bool GetKeytime();
		void UpdateKeytime(const float& dt);
		void Update(const sf::Vector2f& MousePos, const float& dt);
		void Render(sf::RenderTarget& target);
	};
}
#endif // !BUTTON_H

Gui.cpp

#include "Gui.h"

using namespace gui;

Button::Button(float x, float y, float w, float h,
	sf::Font* Font, std::string Text, unsigned CharSize,
	sf::Color TextIdl, sf::Color TextHover, sf::Color TextActive,
	sf::Color Idle, sf::Color Hover, sf::Color Active
   ,sf::Color OutlIdle, sf::Color OutlHover, sf::Color OutlActive, short unsigned Id)
{
	this->bStates = IDLE;
	this->Id = Id;

	this->Shape.setPosition(sf::Vector2f(x, y));
	this->Shape.setSize(sf::Vector2f(w, h));
	this->Shape.setFillColor(Idle);
	this->Shape.setOutlineThickness(1.f);
	this->Shape.setOutlineColor(OutlIdle);

	this->Font = Font;

	this->Text.setFont(*this->Font);
	this->Text.setString(Text);
	this->Text.setFillColor(TextIdl);
	this->Text.setCharacterSize(CharSize);
	this->Text.setPosition(this->Shape.getPosition().x + (this->Shape.getGlobalBounds().width / 2.f) - this->Text.getGlobalBounds().width / 2.f,
						   this->Shape.getPosition().y + (this->Shape.getGlobalBounds().height / 2.f) - this->Text.getGlobalBounds().height / 2.f);
	this->TextIdl = TextIdl;
	this->TextHover = TextHover;
	this->TextActive = TextActive;

	this->Idle = Idle;
	this->Hover = Hover;
	this->Active = Active;

	this->OutlIdle = OutlIdle;
	/*this->OutlHover = OutlHover;
	this->OutlActive = OutlActive;*/
}

Button::~Button()
{
}
//Access
const bool Button::Pressed() const
{
	if (this->bStates == ACTIVE)
		return true;
	return false;
}

const std::string gui::Button::GetText() const
{
	return this->Text.getString();
}
const short unsigned& gui::Button::GetId() const
{
	return this->Id;
}
//Modifier
void gui::Button::SetText(const std::string Text)
{
	this->Text.setString(Text);
}

void gui::Button::SetId(const short unsigned Id)
{
	this->Id = Id;
}

//Functions

void Button::Update(const sf::Vector2f& MousePos)
{
	this->bStates = IDLE;

	if (this->Shape.getGlobalBounds().contains(MousePos)) {
		this->bStates = HOVER;
		if (sf::Mouse::isButtonPressed(sf::Mouse::Left)){
			this->bStates = ACTIVE;
		}
	}
	switch (this->bStates)
	{
	case IDLE:
		this->Shape.setFillColor(this->Idle);
		this->Text.setFillColor(this->TextIdl);
		this->Shape.setOutlineColor(this->OutlIdle);
		break;
	case HOVER:
		this->Shape.setFillColor(this->Hover);
		this->Text.setFillColor(this->TextHover);
		this->Shape.setOutlineColor(this->OutlHover);
		break;
	case ACTIVE:
		this->Shape.setFillColor(this->Active);
		this->Text.setFillColor(this->TextActive);
		this->Shape.setOutlineColor(this->OutlActive);
		break;
	default:
		this->Shape.setFillColor(sf::Color::White);
		this->Text.setFillColor(sf::Color::Blue);
		this->Shape.setOutlineColor(sf::Color::Green);
		break;
	}
}

void Button::Render(sf::RenderTarget& target)
{
	target.draw(this->Shape);
	target.draw(this->Text);
}

//-------------DrpList---------------
gui::DrpList::DrpList(float x, float y, float w, float h, sf::Font& Fnt, std::string List[], unsigned NumElemnt, unsigned DefIndex)
	:Fnt(Fnt), ShowList(false), KeytimeMax(10.f), Keytime(0.f)
{
	//unsigned NumElemnt = sizeof(List) / sizeof(std::string);
	this->ActivElmnt = new gui::Button(
		x, y, w, h,
		&this->Fnt, List[DefIndex], 12,
		sf::Color(255, 255, 255, 150),
		sf::Color(255, 255, 255, 200),
		sf::Color(20, 20, 20, 50),
		sf::Color(70, 70, 70, 200),
		sf::Color(150, 150, 150, 200),
		sf::Color(20, 20, 20, 200),
		sf::Color(255, 255, 255, 200)
		sf::Color(255, 255, 255, 255),
		sf::Color(20, 20, 20, 200));

	for (size_t i = 0; i < NumElemnt; i++) {
		this->List.push_back(new gui::Button(
			x, y + ((i + 1) * h), w, h,
			&this->Fnt, List[i], 12,
			sf::Color(255, 255, 255, 150),
			sf::Color(255, 255, 255, 255),
			sf::Color(20, 20, 20, 50),
			sf::Color(70, 70, 70, 200),
			sf::Color(150, 150, 150, 200),
			sf::Color(20, 20, 20, 200),
			sf::Color(255, 255, 255, 0)
			sf::Color(255, 255, 255, 0),
			sf::Color(20, 20, 20, 0),i));
	}
}
	

gui::DrpList::~DrpList()
{
	delete this->ActivElmnt;
	for (size_t i = 0; i < this->List.size(); i++) {
		delete this->List[i];
	}
}

const bool gui::DrpList::GetKeytime()
{
	if (this->Keytime >= this->KeytimeMax) {
		this->Keytime = 0.f;
		return true;
	}
	return false;
}

void gui::DrpList::UpdateKeytime(const float& dt)
{
	if (this->Keytime < this->KeytimeMax)
		this->Keytime += 10.f * dt;
}

//DrpList
void gui::DrpList::Update(const sf::Vector2f& MousePos , const float& dt)
{
	this->UpdateKeytime(dt);
	this->ActivElmnt->Update(MousePos);
	//Show - hide list
	if (this->ActivElmnt->Pressed() && this->GetKeytime()) {
		if (this->ShowList)
			this->ShowList = false;
		else this->ShowList = true;
	}

	if (this->ShowList) {
		for (auto& i : this->List) {
			i->Update(MousePos);

			if (i->Pressed() && this->GetKeytime()) {
				this->ShowList = false;
				this->ActivElmnt->SetText(i->GetText());
				this->ActivElmnt->SetId(i->GetId());
			}
		}
	}
}

void gui::DrpList::Render(sf::RenderTarget& target)
{
	this->ActivElmnt->Render(target);
	if (this->ShowList) {
		for (auto& i : this->List) {
			i->Render(target);
		}
	}
}

Settings.h

#pragma once
#ifndef SETTINGS_H
#define SETTINGS_H

#include "State.h"
#include "Gui.h"

class Settings :
	public State
{
private:
	//Vars
	sf::Font Fnt;
	sf::Texture BgTex;
	sf::RectangleShape BackGrnd;

	std::map<std::string, gui::Button*> buttons;
	std::map<std::string, gui::DrpList*> drplist;
	gui::DrpList* Dl;

	//Functions
	void InitVars();
	void InitBackGrnd();
	void InitFonts();
	void InitKeybinds();
	void InitGui();

public:
	Settings(sf::RenderWindow* window, std::map<std::string, int>* SupportedKeys, std::stack<State*>* states);
	virtual~Settings();
	//Access
	//Funcs
	void UpdateInput(const float& dt);
	void Update(const float& dt);
	void UpdateGui(const float& dt);

	void RenderGui(sf::RenderTarget& target);
	void Render(sf::RenderTarget* target = nullptr);
};
#endif // !SETTINGS_H

Settings.cpp

#include "Settings.h"

//Init Funcs
void Settings::InitVars()
{

}

void Settings::InitBackGrnd()
{
	this->BackGrnd.setSize(
		sf::Vector2f(
			static_cast<float>(this->window->getSize().x),
			static_cast<float>(this->window->getSize().y)));

	if (!this->BgTex.loadFromFile("Resources/Images/BackGrounds/Menu/M2.png")) {
		throw "Error:Main_Menu:Failed to load background texture";
	}
	this->BackGrnd.setTexture(&this->BgTex);
}

void Settings::InitFonts()
{
	if (!this->Fnt.loadFromFile("Fonts/SPACEMAN.ttf")) {
		throw("Error:Main Menu St::Couldn't load font");
	}
}

void Settings::InitKeybinds()
{
	std::ifstream ifs("Config/MMKeys.ini");

	if (ifs.is_open()) {
		std::string key = "";
		std::string key2 = "";
		int keyval = 0;
		while (ifs >> key >> key2)
		{
			this->Keybinds[key] = this->SupportedKeys->at(key2);
		}
	}
	ifs.close();

	this->Keybinds["CLOSE"] = this->SupportedKeys->at("ESC");
	this->Keybinds["Left"] = this->SupportedKeys->at("A");
	this->Keybinds["Right"] = this->SupportedKeys->at("D");
	this->Keybinds["Up"] = this->SupportedKeys->at("W");
	this->Keybinds["Down"] = this->SupportedKeys->at("S");
}

void Settings::InitGui()//Lnk2019
{
	this->buttons["Exit"] = new gui::Button(
		900.f, 880.f, 250.f, 50.f,
		&this->Fnt, "Back", 50,
		sf::Color(70, 70, 70, 200),
		sf::Color(150, 150, 150, 250),
		sf::Color(20, 20, 20, 50),
		sf::Color(70, 70, 70, 0),
		sf::Color(150, 150, 150, 0),
		sf::Color(20, 20, 20, 0), sf::Color(70, 70, 70, 0));
	std::string Li[] = {"1920x1080","800x600","640x480"};
	this->drplist["Resolution"] = new gui::DrpList(800, 450, 200, 50, Fnt, Li, 3);
}

Settings::Settings(sf::RenderWindow* window, std::map<std::string, int>* SupportedKeys, std::stack<State*>* states)
	:State(window,SupportedKeys,states)
{
	this->InitVars();
	this->InitBackGrnd();
	this->InitFonts();
	this->InitKeybinds();
	this->InitGui();
}

Settings::~Settings()
{
	auto it = this->buttons.begin();
	for (it = this->buttons.begin(); it != this->buttons.end(); ++it) {
		delete it->second;
	}
	auto it2 = this->drplist.begin();
	for (it2 = this->drplist.begin(); it2 != this->drplist.end(); ++it2) {
		delete it2->second;
	}
}


//Access
//Funcs 
void Settings::UpdateInput(const float& dt)
{
}

void Settings::Update(const float& dt)
{
	this->UpdateMousePos();
	this->UpdateInput(dt);

	this->UpdateGui(dt);

	std::cout << this->MousePosView.x << " " << this->MousePosView.y << "\r";
}

void Settings::UpdateGui(const float& dt)
{	//Update guis and handle their functions
	for (auto& it : this->buttons) {
		it.second->Update(this->MousePosView);
	}
	//Quit
	if (this->buttons["Exit"]->Pressed()) {
		this->Endstate();
	}

	//Drop List
	for (auto& it : this->drplist) {
		it.second->Update(this->MousePosView, dt);
	}
	
}

void Settings::RenderGui(sf::RenderTarget& target)
{
	for (auto& it : this->buttons) {
		it.second->Render(target);
	}

	for (auto& it : this->drplist) {
		it.second->Render(target);
	}
}

void Settings::Render(sf::RenderTarget* target)
{
	if (!target)
		target = this->window;
	target->draw(this->BackGrnd);

	this->RenderGui(*target);
}

The full error message:
'
Error LNK2019

unresolved external symbol "public: __thiscall gui::Button::Bu tton(float,floa t,float,float,c lass sf::Font *,class std::basic_stri ng<char,struct std::char_trait s<char>,class std::allocator< char> >,unsigned int,class sf::Color,class sf::Color,class sf::Color,class sf::Color,class sf::Color,class sf::Color,class sf::Color,class sf::Color,class sf::Color,unsig ned short)" (??0Button@gui@ @QAE@MMMMPAVFon t@sf@@V?$basic_ string@DU?$char _traits@D@std@@ V?$allocator@D@ 2@@std@@IVColor @3@22222222G@Z) referenced in function "private: void __thiscall Settings::InitG ui(void)" (?InitGui@Setti ngs@@AAEXXZ)

Project:
Star Fire

File:
F:\Star Fire SFML\Star Fire\Settings.o bj

Line:
1
'


Everything works perfectly before video 48,a Lnk2019 occurs right after i put more parameters into the 'gui::Button(); ' constructor in 'Gui.cpp' specifically the 'sf::color::' OutlIdle - Hover and Active parameters. As soon as i put them in the error occurs.

Can someone help me ?