so i am following tic tac toe tutorial on youtube. now i have wrote all the code from the state machine to the states but i decided instead of starting with a splash screen i’d go straight to the main menu. I’m trying to add the state to the stack but it gives me this error:

”Error (active) object of abstract class type "HoodiniGames::MainMenu" is not allowed”

here is my mainmenu.h

namespace HoodiniGames {

class MainMenu: public State
{
public:
 MainMenu(gamedataRef data);
 ~MainMenu();
 void init();
 void update(float dt);
 void HandleInput();
 void draw(float dt);

 void moveUp();
  void moveDown();
 int getpressedItem() { return selectedindex; }
 void setPressedItem(int index) { selectedindex = index; }
  sf::RectangleShape getexitgameButton() { return exitGame; };

 private:
 int selectedindex;
 sf::Font font;
 sf::Text text[MAX_NUMBER_ITEMS];
 sf::RectangleShape singlePlayer;
 sf::RectangleShape multiPlayer;
 sf::RectangleShape exitGame;
 sf::Event event;
 gamedataRef _data;

};

}

i try creating the object in the game.cpp

 namespace HoodiniGames
 {
HoodiniGames::Game::Game(int width, int height, string title)
{
    _data->window.create(sf::VideoMode(width, height), title, sf::Style::Close | sf::Style::Titlebar);

    _data->state.AddState(stateRef(new MainMenu(_data)),true);//<----  error occurs here 

    this->Run();
}

the mainmenu class inherits from the state (which is a abstract class) so why is the mainmenu recognized as an abstract class