How do I correctly bind keys using the command pattern?-CodePudding

I've been working on a game using c and sfml and I've been trying to implement the command pattern as seen in the link below: https://gameprogrammingpatterns.com/command.html. More specifically, I am trying to implement the command pattern so that it can be used for any character in the scene.

I've set up a general command class:

class Command
{
public:
    ~Command();
    virtual void execute(Character& character) = 0;

};

And then a bunch of classes that inherit from this class, for example:

#include "Command.h"

class WalkDownCommand : public Command
{
public:
    virtual void execute(Character& character) override
    {
        character.walkDown();
    }
};

Then I created a character class that contains all the functions for walking, and a shape to represent it's body:



#include <SFML\Graphics.hpp>


class Character {

public:
    Character();
    ~Character();

    void draw(sf::RenderWindow* renderWindow);
    void walkRight();
    void walkLeft();
    void walkUp();
    void walkDown();
private:
    sf::CircleShape* tempShape;

};

These functions are then called using their respective command Class. I've also created a HandleInput function that checks whether a key is pressed and returns a reference to a specific command object:

#include "Command.h"

class InputHandler
{
public:

    Command* handleInput();
    
private:
    Command* W_KEY;
    Command* A_KEY;
    Command* S_KEY;
    Command* D_KEY;

};

The handleInput function looks as follows:

Command* InputHandler::handleInput()
{
    if (sf::Keyboard::isKeyPressed(sf::Keyboard::W))
    {
        std::cout << "W key is pressed" << std::endl;
        return W_KEY;
    }
    if (sf::Keyboard::isKeyPressed(sf::Keyboard::A))
    {
        std::cout << " A key is pressed" << std::endl;
        return A_KEY;
    }
    if (sf::Keyboard::isKeyPressed(sf::Keyboard::S))
    {
        std::cout << "S key is pressed" << std::endl;
        return S_KEY;
    }
    if (sf::Keyboard::isKeyPressed(sf::Keyboard::D))
    {
        std::cout << "D key is pressed" << std::endl;
        return D_KEY;
    }

    return NULL;
    
}

In the games main loop, I created a Command pointer object that calls the handleInput function to check for input. If it finds a command, it executes this command ('gloon' is the object of type Character):

Command* command = inputHandler.handleInput();
        if (command)
        {
            command->execute(gloon);
        }

When running this, the handleInput function gets correctly called and then returns one of the pressed keys. However, the program crashes right after, stating: Exception thrown: read access violation. command was 0xFFFFFFFFFFFFFFFF.

In the link I showed of the beginning of the page, the command pattern description also states that I need to bind the Command* objects to the correct function. This might be what is causing the issue, but I'm having trouble to understand how to do this. Any help is appreciated!

CodePudding user response：

Maybe, try something like this (to initialize pointers in your class InputHandler):

    #include "Command.h"
    
    class InputHandler
    {
    public:
        InputHandler()
        { 
            W_KEY = new WalkUpCommand; 
            A_KEY = new WalkLeftCommand; 
            D_KEY = new WalkRightCommand; 
            S_KEY = new WalkDownCommand;
        }
        ~InputHandler() 
        {
            delete W_KEY;
            delete A_KEY;
            delete S_KEY;
            delete D_KEY;
        }
        Command* handleInput();
        
    private:
        Command* W_KEY;
        Command* A_KEY;
        Command* S_KEY;
        Command* D_KEY;
    
    };

I'm not sure, but hope it will be helpful