无效使用非静态数据成员c ++

Question

I've taken a look at the wide variety on answers to questions starting with the same title as this, but to no avail so unfortunately I'm having to post my own version. I'll try explain as comprehensively as I can. The error I'm getting is as follows

error: invalid use of non-static data member 'MainState::pellet'

This error relates to a function in a Player class file which is attempting to access the members of an array of 5 Pellet class objects declared in another file. Here's the function which is causing the error:

    void Player::onCollide(std::list<Entity*>& entityList)
{

    //create two iterators so can do self-checks
    std::list<SnakePieces>::iterator i;
    std::list<SnakePieces>::iterator m;


    //collision with pellet
    for(Entity* player : entityList)
    {
        Player* p = dynamic_cast<Player*>(player);

        if(p)
        {
            i=p->Snake_List.begin();
            for(int t=0; t < 4; t++)
            {
                if(i->x==MainState::pellet[t]->x)
                {

                    return;
                }

            }

        }


    }

//all collisions for the first snake
    auto itPlayer = entityList.begin();
    Player* p = dynamic_cast<Player*>(*(itPlayer++));
    Player* p2 = dynamic_cast<Player*>(*itPlayer);
    if(p)
    {
        if(i != m)
        {
            i=p->Snake_List.begin();
            for(m=p2->Snake_List.begin(); m != p2->Snake_List.end(); m++)
            {
                if ((i->x == m->x) && i->y == m->y)
                {
                    p->respawn();
                    return;
                }
            }
        }
    }

The array is declared in the MainState class header file and that looks like this:

class MainState : public prg::IAppState,
    public prg::ITimerEvent
{
public:
    void onRender( prg::Canvas& canvas ) override;
    void onTimer(prg::Timer & Timer) override;
    void checkBoundaries();


    Pellet* pellet[5] {new Pellet(), new Pellet(), new Pellet(), new Pellet(), new Pellet()};
private:

    //timers
    prg::Timer Timer {0, 150, *this};
    prg::Timer Spawn_Timer {1, 5000, *this};

    //players & pellets
    std::list<Entity*>     players_ { new HumanPlayer( "Solid Snake"), new HumanPlayer ( "Liquid Ocelot")};



    //images
    prg::Image  background_;

    //bools
    bool newPlayer = false;
    bool timerRunning = false;


};

I've cut out a great deal of code unrelated to the problem, but I just can't get my head around what the issue is and why I can't access this data. I'm pretty new to a lot of c++ so I know I've done something wrong or haven't implemented something here, but can't see what despite reading similar questions for a good hour or so, sorry. Hopefully someone can shine some light on this, thanks!

Answer 1

As the error says, pellet is a non-static member of MainState ; so you can only access it as part of a MainState object. You are trying to access it as if it were a static member, which exists independently of any objects.

If your Player class needs to access it, then it will need a reference to it, or to the MainState object that contains it.