抽象类中的C ++ equal方法

Question

I'm developing a chess game. So, I created an abstract class called Piece and the real pieces implement this class, So I have concrete classes like Pawn, Rook...

The problem is: I need an equal method in the interface to compare two pieces. I'm having problem to it, because I wanted a polimorfic method, that is, a method that could compare a piece to any piece. The problem is I can't declare "Piece o" as an argument to the method cause Piece is an abstract type. How can I do this in C++?

I have the following code:

class Piece
{
public:
    virtual ~Piece();

    virtual std::string name() = 0;
    virtual Color color() const = 0;
    virtual Type type() const = 0;
    virtual Position position() const = 0;
    virtual void moveToPosition(Position p) = 0;
    virtual bool isValidMove(Position np, Board &b) = 0;
    virtual vector<Movimento>& generateMoves(Board &t) = 0;
    virtual bool equal(Piece &o) = 0;
};

Answer 1

maybe do something like

virtual bool operator==(const Piece&) = 0;

no object slicing, u can compare the type and other information..

or you can just implement it in your Piece class, such as

virtual bool operator==(const Piece& rhs) {
    if (this.type() == rhs.type()) {
        return true;
    }
    else {
        return false;
    }
}

---

actually, you probably don't need operator== overloaded, but instead just a equal method...

Answer 2

I solved my problem changing the defition of Piece to an Abstract class instead of a Interface (in the Java vocabulary). Now my code is less redundant and clearer.

class Piece
{
protected:
    std::string m_Name;
    Color m_Color;
    PieceType m_PieceType;
    Position m_Position;

public:
    Piece(std::string n, Color c, PieceType t, Position p) :
          m_Name(n), m_Color(c), m_PieceType(t), m_Position(p){};
    virtual ~Piece();

    std::string name() const;
    Color color() const;
    PieceType pieceType() const;
    Position position() const;
    bool equal(const Piece&) const;
    virtual void moveToPosition(Position p) = 0;
    virtual bool isValidMove(Position np, Board &t) = 0;
    virtual vector<Move>& generateMoves(Board *b) = 0;
};