C++ Instances VS pointers VS references

Question

I've a program which creates many instances of my own Class. Then I operate them: read, change, pass them to some third party methods etc.

There are three questions.

1. Do I store an vector of instances or a vector of pointers? Why?

2. If I do not want to change an instance do I pass to the function an instances or pointers to it? Why?

3. If I do want to change an instance, do I pass a pointer or a reference? Why?

Thanks in advance!

Class example:

class Player {
    public:
        static const char               width = 35;
        static const char               height = 5;
        static const char               speed = 15;

        int                             socketFD;
        float                           xMin;
        float                           xMax;

        char                            status;
        float                           x;
        float                           y;
        char                            direction;

                                        Player ( int );
        void                            Reset();
        void                            Move();
        void                            SetHost();
        void                            SetClient();

    private:
        void                            EscapeCheck();
};

Answer 1

Do I store an array of instances or an array of pointers? Why?

If Class is a base class, and you want to prevent object slicing, you store pointers. Otherwise, objects.

If i do not want to change an instance do I pass to the function an instances or pointers to it? Why?

If you pass by value, you don't modify the original object because you're working on a copy. If you pass a pointer or a reference, you mark it as const:

void foo ( MyClass const* );
void foo ( MyClass const& );

If i do want to change an instance, do i pass a pointer or a reference? Why?

Either. I personally prefer references, pointers are more tightly connected to dynamic allocation.

Nowadays, RAII is often used, so an excellent alternative is to use smart pointers instead.